Annual Report 1949

National Bureau

of Standards

Miscellaneous Publication 198
I V I
UNITED STATES DEPARTMENT OF COMMERCE

Charles Sawyer, Secretary

NATIONAL BUREAU OF STANDARDS

E. U. Condon, Director

Annual Report 1949

National Bureau

of

Standards

Miscellaneous Publication 198

For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price 75 cents

CONTENTS

1 . General Review

Page

1

2. Electricity and Optics 3 Maintenance of the standard ohm 3, Precision electrothermic voltmeter for audio frequencies 5, Improved magnetic permeameter 5, Surge-voltage

measurements 6, New calibration system for camera lenses 6, Testing

of photogrammetric lenses 8, Standards for calibration of photoelectric

colorimeters 8, Sensitometry of diazo papers 8, Index of refraction of new infrared materials 9.

3. Metrology.

The standard meter 10, Unification of screw thread standards 10, Dental

materials 13, Viscosity and flow of gases 13.

10

4. Heat and Power

Thermometry 14, Thermodynamics 15, Low-temperature physics 17, Gas

turbines and jet engines 18.

13

5. Atomic and Radiation Physics 19

Magnetic moment of the proton 19, Spectra of fission products 20, Semiconductors 21, Cathode emission processes 22, Radioactivity 22, Protection

against radiation 23, X-ray equipment for medical use 23, Mass spectrometry 24, Properties of magnetic-type electron lenses 25, Electron-optical

shadow method 25.

:6.. Chemistry .» - 27

Properties of soaps 27 , Fundamental chemistry of sugars 28 , Infrared spectrometry 28, Properties of corn products 29, Paints, varnishes, and lacquers 29,

Dissociation constants of organic compounds 29, Hydrocarbons 30, Thermochemistry 30, Gas-burning appliances 31, Electrodeposition 31, Redetermination of the faraday 32, Spectrochemical analysis 33, Pure substances 33.

7. Mechanics 31

Pfund sky compass 35, Talking books for the blind 35, Electric twinning of quartz 36, Sound transmission through walls 36, Boundary layer investigations 37, Vacuum-tube accelerometer 37, Capacities of plumbing stacks and

drains 38, Flow of stratified liquids 38, Investigation of water waves 39.

8. Organic and Fibrous Materials 39

Nature of adhesion 40, Fire-retardant coatings for aircraft 41, NBS method

for microsectioning 41, Shrinkage of collagen 43, Impregnation of sole leather with rubber 43, Aging of plastics and rubbers 43, Refractive index

of natural rubber 44, Photochemistry of cellulose 44, Infrared analysis of

cellulose 44.

9. Metallurgy ; 45

Corrosion 46, Melting and casting of metals 47, Failure of metals in

service 47.

Ill
Pago

10. Mineral Products 48

Synthetic mica 48, Ceramic coatings for jet engines 49, Ceramic dielectrics 49, High-temperature phase-equilibrium studies 50, Optical glass 50

Durability of building stone 50, Flow table for cement testing 51, Vitrified china 51, Service testing of porcelain enamel 52.

11. Building Technology 53

Reinforcing bars for concrete 53, Heat transfer in buildings 54, Fire protection 54, Thermal conductivity at high temperature 54, Bituminous

vapor-barrier materials 55, Codes and specifications 55.

12. Applied Mathematics 56

Numerical analysis 56, Mathematical tables 57, Statistical engineering 58.

13. Electronics. 58

Electron tubes 59, Electronic miniaturization and printed circuits 59,

Electronic instrumentation 61, Parachute telemetering unit 62, Characteristics of electrocardiographs 63.

14. Automatic Computing Machines 63

15. Radio Propagation 65

Atomic clock 66, Microwave standards 69, Ionospheric research 70, Tropospheric propagation 71.

16. Testing, Calibration, and Standard Samples 72

Electricity and optics 74, Metrology 75, Heat and power 75, Atomic and

molecular physics 76, Chemistry 76, Mechanics 76, Organic and fibrous

materials 78, Metallurgy 79, Mineral products 79, Building Technology 79, Electronics 80, Radio propagation 81.

17. Technical Services and Cooperation 81 Advisory services 82, Federal specifications 83, Mathematical problems 83, Building technology 84, Organic and fibrous materials 86, Mineral products 86, Commodity standards 87, Weights and measures 89,

Research associate program 90, Scientific and technical groups 91, Inter- national radio conferences 92, International Commission on Illumination 93, International Conference on Weights and Measures 93, Office of International Relations 93, Technical sessidn on bone char research 94.

Scientific and Technical Divisions and Sections 96

IV
1. General Review

As the principal agency of the Federal Government for fundamental research in physics, mathematics, chemistry, and engineering, the National

Bureau of Standards carries on a large number and variety of projects in

these fields. It acts as custodian of the national standards of physical meas- urement and conducts the necessary research leading to improvement 'in such standards and measurement methods. It investigates problems in

basic science, undertakes major applied research and development programs, develops improved methods for testing materials and equipment, determines physical constants and properties of materials, develops specifications for Federal supplies, and serves in an advisory capacity on many scientific and technical matters in the physical sciences.

Most of the Bureau's work was conducted at its laboratories in Washington. Six materials testing stations, chiefly concerned with cement analysis, were maintained in Allentown, Pa.; Permanente, Calif.; Seattle, Wash.;

Riverside, Calif.; Denver, Colo.; and San Francisco, Calif. Two proving

grounds were in use during the year (one in Maryland, the other in New

Jersey) . A railway-scale test-car station was maintained in Clearing, 111. Research in certain fields of applied mathematics was conducted at the

Bureau's Institute for Numerical Analysis, Los Angeles, Calif. Radio propagation activities involved the maintenance of field stations at Sterling,

Fort Belvoir, and Hybla Valley, Va. ; Puunene and Palmyra Island, Territory of Hawaii; Guam; Trinidad, British West Indies; White Sands Proving

Ground, Las Cruces, N. Mex., and Anchorage, Alaska. Eleven other radio

propagation field stations were under contract to the Bureau. In addition,

two transmitting stations were operated: WWV at Beltsville, Md., and

WWVH in Hawaii.

The research and development work of the Bureau is primarily of two

kinds. There are, first, the investigations that result from the Bureau's

responsibility for fundamental measurements in the physical sciences, the

development and maintenance of primary standards in science and engineering, and the testing and calibration of standard measuring apparatus and

reference standards. In these fields, research and development are mainly

directed toward greater precision in measurements concerned with the Nation's fundamental scientific standards, physical constants, and properties

1
of substances and materials. At the same time, however, new standards

and measurements of this general type must be investigated and developed

as new fields of science open, such as atomic and nuclear physics, the higher

frequencies in radio propagation, and the chemistry of high polymers. A

second phase of research and development at the Bureau consists of largescale specific projects undertaken either under direct congressional authorization or for other Government agencies. Examples of the former are the

work in artificial radioactivity, building technology, and high polymers;

examples of the latter include guided missiles, ordnance electronics, jet engines and fuels, electronic computing machines, numerical analysis, and

many of the projects relating to aeronautics.

The following three activities of the Bureau—technical and consulting

services, national cooperation, and international cooperation—stem directly or indirectly from the preceding functions and responsibilities of the Bureau.

The results of the Bureau's investigations, combined with the knowledge of

its specialists in some 100 fields within the physical sciences and mathematics, are at the disposal of the Government. Accordingly, extensive

technical and consulting services are provided to other Government agencies.

During the course of the year, every major agency of the Federal Government, hundreds of bureaus and offices, a large number of States, and many

county and municipal governments called on the Bureau for technical aid.

Cooperation of a national nature is extended to scientific and technical

societies, groups, and organizations, to industries, private laboratories, and

universities. An important aspect of this cooperation has to do with scientific and technical standards, many of them related to products and equipment, safety problems, and codes. The Bureau cooperates with such groups

for several reasons: the Government, as the largest single purchaser in the

world, has a direct interest in this work; the Bureau is able to contribute

certain types of information not available elsewhere; and the Bureau itself

profits from the knowledge it gains of developments outside its own laboratories. International cooperation is based largely on the role of the Bureau

as the technical spokesman for the United States on international agreements relating to the development and establishment of international

scientific standards.

The scientific activities of the Bureau during the fiscal year 1949 were carried out through 13 scientific divisions concerned with electronics, applied

mathematics, atomic and radiation physics, radio propagation, electricity

and optics, metrology, heat and power, chemistry, mechanics, organic and

fibrous materials, metallurgy, mineral products, and building technology. A

fourteenth division was concerned with commodity standards and with the

coordination of the Bureau's work for the Federal Specifications Board. The

remainder of this report attempts to suggest the nature and scope of the

Bureau's work through examples of typical projects. Only a small proportion of all projects can actually be covered in this way, but the topics discussed have been chosen as representative of the over-all program.

2
Left: this high-precision spectrometer determines the refractive index of trans- parent materials used by the Bureau in standardizing industrial refractometers.

Right: a new precision camera calibrator recently developed by the Bureau is

)| tested for accuracy (p. 8).

The work in electricity and optics is for the most part closely connected

with problems of measurement in these fields and relates to the establishment

of units of measurement, the development of improved or new methods of

measurement, the design of improved or new standard apparatus, the development of standards for issuance, and studies of the properties of

materials.

The electrical work includes the establishment and maintenance of the

units of resistance and voltage; their application in the development of

standard apparatus for measuring inductance, capacitance, electric current,

power, energy, magnetizing force, and magnetic induction ; and the dissemination throughout the Nation of standard values of these quantities. The

work in optical standards and measurements includes problems of luminous

intensity and flux; spectrophotometry, color, transmittance, reflectance,

opacity and gloss; refractive index, focal length and resolution of lenses,

cameras, and other optical systems; and sensitivity and contrast of photographic emulsions. In recent years microcopying of documents to conserve

space and to insure permanence of records has grown to such an extent that

the development and maintenance of standards of quality for these materials has become important. The following projects illustrate the type of

work carried forward or completed during the year.

Maintenance of the Standard Ohm

The unit of electrical resistance, the ohm, is defined in terms of the units

of length and time and the permeability of free space. The measurement

of resistance in terms of these units is very difficult and is carried out only for

tne purpose of calibrating standards of resistance for national standardizing

s, 2. Electricity and Optics

3
Recent developments in gas turbines and jet engines have given rise to urgent

need for research on problems concerned with combustion, control of fuel supply,

and measurement of the temperature, composition, and thermal properties of

exhaust gases (p. 18). Above: general view of combustion research laboratory.

Below: interior of the combustion room showing three burner channels for

combustion research.

4
laboratories. These standards are then used for calibrating working standards submitted by industry and private laboratories.

Between measurements of the national standards in terms of length, time,

and permeability, it has been assumed that they have remained constant.

Heretofore there has been no way to check this assumption, for only relative

values of the standards could be determined. However, as an outgrowth

of a recent elaborate measurement of resistance at the Bureau in terms of

length, time, and permeability, it has now been found practicable to make

frequent tests of the national standards, thus insuring their stability with

time. This is done by a method developed at the Bureau for the measure- ment of resistance in terms of a mutual inductor. The dimensions of the

inductor can be measured from time to time, and any change in inductance can be calculated from the change in dimensions. Comparison of the

standard resistors with the inductor reveals any change in the values of the

standard resistors. This method is so accurate that changes in resistance

of a few parts in a million can be detected.

Precision Electrothermic Voltmeter for Audio Frequencies

To meet the need for greater accuracy of measurement in the audiofrequency range, new equipment has been completed and installed, permitting measurements of audio-frequency voltage with an accuracy

approaching one part in 10,000. The equipment makes use of an insulated thermoelement whose heater is in series with a resistance used as a multiplier to extend its voltage range. It incorporates a simple Lindeck

potentiometer which provides precise measurements of the thermal electromotive force produced by the thermoelement (selected to have negligible

frequency error), thus permitting calibration on direct voltage. Associated equipment for current measurements to 50 amperes over the same

frequency range is being installed.

Improved Magnetic Permeameter

The development of an improved magnetic permeameter for magnetizing forces up to 300 oersteds has been completed. The instrument is

absolute in principle—i. e., its constants are derived from its own dimensions

so that calibration by reference to any other permeameter is not required.

The new instrument, called the M H permeameter, has an accuracy at

least comparable to that of the Burrows permeameter, which for many years

has been the accepted standard, yet it is much simpler to operate. Moreover, it requires only a single specimen, whereas the Burrows permeameter

requires duplicate specimens, one of which is used as an auxiliary. The

new permeameter will be adopted as the standard instrument for magnetic

testing at magnetizing forces up to 300 oersteds.

5
Surge-Voltage Measurements

Work continued on the project for improving front-of-wave surge-voltage

measurements at intervals less than 1 microsecond. To this end, a large

high-voltage electrode has been constructed to provide shielding and voltage

grading of the space to be occupied by a resistance voltage divider.

Measurements on a number of commercially available resistors revealed

that they had excessive voltage coefficients and would not be suitable for

this work. A promising resistor construction was therefore developed, consisting of a thin nichrome strip folded back and forth on itself with 1-mil

insulation between folds. This resistor has a low voltage coefficient and

constant effective resistance up to several megacycles. In experimental

tests, the usual reverse-wound resistance cards (flat cards with one clockwise

and one counterclockwise winding connected in parallel) were found to be

properly shielded and to have satisfactory field grading when assembled

in the shielded and graded space under the large high-voltage electrode.

New Calibration System for Camera Lenses

The method now in general use for designating the speed of a photographic lens is based entirely upon the ratio of the equivalent focal length

of the lens to the diameter of the aperture. This ratio—known as the

/-number—gives no consideration to the great differences in the useful

light transmitted by various lenses. These difference are the result of absorption in the glasses of which the lens elements are made, or reflection and

scattering at the surfaces. The introduction of reflection-reducing coatings

has accentuated the inconsistencies of the present method to such an extent

that for a given /-number the light transmitted by two lenses may differ

almost by 100 percent. While this is a disadvantage in all photographic

work, it is probably most costly to the motion-picture industry because of the

large amount of film exposed each year and the additional expense of talent

for retakes.

Recently the Bureau devised a new system of calibrating lenses which

involves only a photometric measurement and eliminates the inconsistencies

of the present system. The Society of Motion Picture Engineers has

adopted the Bureau's calibration system, and the new method of lens

marking will be used for professional motion picture cameras. Sixteenmillimeter cameras for amateurs and one type of still camera are now

available commercially with the new system. It is expected that the new

method of lens calibration will be embodied in specifications for still cameras and will be made generally available on all of the more expensive cameras.

6
Laboratory studies of the fundamental physical and clinical properties of dental

materials are conducted at the Bureau (p. 13). Top: tendencies toward shrinkage

in dental amalgam are determined by means of the dental interferometer. Lower

left: to obtain data on materials and techniques, experimental dentures are processed under controlled conditions. Lower right: measurement of shrinkage in a plastic denture.
Testing of Photogrammetric Lenses

Photogrammetry, the science of making maps from airplane photographs

(introduced shortly after World War I), is now one of the most important

methods of map making, of great value for both military and civilian

mapping purposes. Its applications include small-scale mapping of continental areas, large-scale mapping of small sites to aid in the placing of

manufacturing establishments, mapping for tax purposes, and many other

uses.

If maps made from airplane photographs are to be accurate, the errors of the camera lenses must be precisely determined and compensated for. The National Bureau of Standards is responsible for the necessary tests on the lenses and for certifying those which can be satisfactorily used for

mapping. For many years these tests have been made with special test- ing equipment designed and constructed at the Bureau. However, this

equipment tests the field of the lens along only one diameter at a time. Be- cause of the greater volume of work required and the demand for increased

accuracy, a new instrument has now been developed at the Bureau which

enables the field of the lens to be tested simultaneously at 25 points located on two diameters. Tangential distortion, a source of error which has

recently received increased attention, can be measured on this new

apparatus.

Standards for Calibration of Photoelectric Colorimeters

A number of complicated processes are employed in the refining of petroleum to produce gasoline, kerosine, and lubricating oils and greases. Measurements of the color of the product are used to follow the progress of these

processes and also as a basis for the purchase and sale of petroleum products

in various stages of refinement. To aid in this work, the petroleum industry, through ASTM Committee D-2, has been engaged since 1942 in the

development of a photoelectric method for determining a color index for

petroleum products. The Bureau has cooperated in this development by

supplying permanent color standards, in the form of 2-inch squares of glass,

to calibrate the photoelectric colorimeters. By use of these standards, all photoelectric colorimeters may be adjusted to read on the same basis so that

the purchase and sale of partially refined petroleum may go forward on a

fair and equitable basis without costly disputes.

Sensitometry of Diazo Papers

Diazo papers have largely replaced blueprint papers because they give a

direct positive instead of a negative and because the processing is rapid and

simple. The more popular of these papers is the "dry-developing" type, in

which there is practically no shrinkage or change of the dimensions of the

copy from that of the original. Because the variation in quality of diazo

8
Left: the velocity of second sound, a unique wavelike type of heat transfer occurring in helium II, was measured at temperatures near absolute zero in the Bureau's low-temperature laboratory (p. 17). Right: mutual inductor constructed

at the Bureau for the absolute measurement of resistance in terms of length,

time, and the permeability of free space (p. 3).

papers is large, it is important that purchase specifications be prepared so that the Government may obtain paper of suitable quality. Studies were

therefore made on the sensitometric characteristics of the papers, such as speed, contrast, maximum density, and keeping qualities. The results of

this work will be incorporated in a Federal specification.

Index of Refraction of New Infrared Materials

For the convenience of designers of optical systems to be used in the

infrared region of the spectrum, the refractivity of truly mixed crystals of

thallium iodide and thallium bromide was computed at wavelength intervals

of 0.5 micron in the range from 1 to 39 microns. The values are based on numerous spectrometer measurements averaged for two prisms and then

adjusted by the method of least squares to fit a Ketteler-Helmholtz dispersion equation. Check measurements on one of these crystals after a 12-

month interval showed no change in index. This material, known as KRS5

during the war, is now being produced in a reasonably homogeneous state.

It is the most transparent of all known optical materials in the wavelength

region from 20 to 39 microns and is of importance in the construction of

optical systems to transmit infrared energy.

9
3. Metrology

Problems of measurement, instrumentation, and standardization, involving the basic concepts of length, mass, time, capacity, and density, constituted the greater part of the work in this area of the Bureau's work. Other

activities included a new and basic reproduction of the standard meter,

investigations of the viscosity and flow of gases, research on dental materials, standardization of screw threads, boiler and turbine research, investigation of a proposed new method of weighing railway cars, standardization

of geodetic tapes, research on the thermal expansivity of solid material, and

development of greater accuracy in the calibration of gage blocks.

The Standard Meter

In 1893 Michelson measured the International Prototype Meter in terms

of the wavelengths of the red radiations of cadmium. Others repeated the

work. During the past year the same radiation was used at the Bureau as a standard to rule a meter interval on a platinum-iridium bar. The interval ruled agrees with the interval on the International Prototype Meter

within a fraction of a wavelength (approximately 0.2 micron). This

achievement is about 10 times more accurate than are the ruled intervals on

our National Prototypes. Of equal importance is the fact that this research

shows that the national and international platinum-iridium standards have

not drifted from their original lengths.

Unification of Screw Thread Standards

On November 18, 1948, delegates and representatives from Government

and industry of Canada, the United Kingdom, and the United States met

at the National Bureau of Standards to sign an accord on unification of the

American and British standard systems of screw threads. The accord,

representing the culmination of 30 years of effort among the three nations,

affirms the unification represented in revised publications of the Interdepartmental Screw Thread Committee of the United States of America and

of the British Standards Institution, the Canadian Standards Association,

and the American Standards Association. These documents fulfill all the

requirements for general interchangeability of threaded products made in

the three countries. Not only is the accord of major significance in ex- panding and facilitating commerce among the cooperating nations, but it

also is an important step toward the further development and extension

of unifying standards in other fields of engineering practice. In June 1949,

the International Organization for Standardization, meeting in Paris, recom- mended that all member nations adopt the unified thread form for metric

as well as for the usual types of screws. In the United States, Subcommittee No. 1 of the A. S. A. Sectional

Committee was charged with the revision of A. S. A. Bl. 1-1935, American

Standard Screw Threads, and with embodying therein the Unified Screw

Threads. This task was accomplished with the active cooperation of the

10
declaration of Slccord

toith respect to the

Unification of hereto breads

pt is htrebg declared that the undersigned, representatives of their (government

and Industrg bodies, charged With the development of standards for scretti

threads, agree that the standards for the Unified hereto threads given in the

publications of the Committees of the British Standards institution, Canadian

Standards association, American Standards association and of the interdepartmental 3creto thread Committee fulfill all of the basic requirements for

general interchangeabilitg of threaded products made in accordance toith ang of

these standards.

JBodics noted above toiil maintain continuous cooperation in the

further development and extension of these standards.

^Signed in Washington, ©. this isth day of Bovcmbcr, 191$, at the

national JSurcau of Standards of the United States.

Ministry of (Trade and Commerce, Dominion of Canada

national Bureau of Standards

H. Department of (Commerce

Interdepartmental hereto "Chread Committee

fflinistru, of «£upplu, United Eingdom

Canadian Standards association

Smcrican Standards association Wat ameritan 3ocietji of Mechanical Engineers

Society of automotive Engineers

Sponsors Council of Bnited States and United

kingdom on the Unification of hereto UChreads

11
Interdepartmental Screw Thread Committee and the National Bureau of

Standards. The Sectional Committee, organized under the procedure of

the American Standards Association, is sponsored by the American Society

of Mechanical Engineers and the Society of Automotive Engineers. The

Unified Standards will be made effective in the departments of the U. S. Government by inclusion in the next revision of National Bureau of Standards Handbook 28, Screw Thread Standards for Federal Services. In the

United Kingdom, the draft of the Provisional British Standard Unified

Threads was prepared by the British Standards Institution in conjunction

with the Inter-Services Technical Panel. The Canadians, with extensive

commercial ties to both the United Kingdom and the United States, participated in the joint conferences and agreed to accept the standards

developed by the British and Americans.

In the past, international trade in goods of all kinds has been seriously

handicapped by the lack of interchangeability of screw thread parts. This

has required the manufacturing nation also to supply and distribute such

parts along with the equipment it wishes to market in a foreign area. Furthermore, the question of the availability of such parts has acted as a psychological deterrent to purchasers of products from other nations. These

limitations on the international commerce of Canada, the United Kingdom,

and the United States will gradually disappear as the unified standards are acted upon by the industries of the three nations in the ensuing years. During the first World War, the experience of the allied American and

British armed forces revealed that the lack of interchangeability of American and British screw threads was a serious problem. In World War II, the high degree of mechanization of all military forces made the problem

even more serious than it had been. American industry was required to supply the British with a large volume of war equipment threaded to the

British specification. This not only led to considerable delay but was eco- nomically disadvantageous. At the same time, American military forces

based in England and using equipment with American threads found difficulties in making necessary replacements.

Since 1918, the National Bureau of Standards has taken the lead in the

development of test methods and standards for screw threads. Largely

as a result of the Bureau's efforts, the Unified Screw Thread Standard was

ultimately formulated and agreed upon in five major and several informal

conferences of representatives of the countries concerned. The present

accord calls for a continuance of future cooperation in the field of screw

thread standardization. Such cooperation has two aspects : first, the extension of the unification to the other English-speaking nations (all of which

use the English system of measurement in manufacture) and, second, the

continued development of standards, which must keep pace with improvements in materials and methods of production and inspection developed in

industry. The reduction of the varieties of fasteners is one of the possibilities which further studies of standards and simplification may yield.

12
Dental Materials

Dental cements have never been satisfactory when mixed by the usual

methods in the humidity and high temperature prevailing in the Tropics.

They do not set properly and cannot be finished with a surface to match the

teeth. Generally they stain and disintegrate in a few weeks or months. Recently techniques have been developed at the Bureau which permit these

cements to be mixed in tropical surroundings with very little more difficulty

than the provision of cold water as a cooling medium. A special container

is used. A patent application, with rights to the Government, is being

filed to cover this development.

Investigation of the fundamental principles involved in the polymerization of acrylic resins—used in making dentures and dental restorations

has continued. Data have been obtained on the effect that temperature,

pressure, rate of curing, presence of impurities, and mold surfaces have on

the properties of the cured resin. These data provide explanations for

many of the difficulties—such as "open bite," shrinkage in repair, incomplete curing, premature polymerization, and discoloration—that have been

encountered in the preparation of dentures and restorations.

The recent commercial development of a method for processing certain

acrylic resins which may be cured at low temperatures has led to the widespread use of these resins in dentistry as restorative materials. Fundamental data on the physical and chemical properties and the curing characteristics of these resins have been obtained. As a result, considerable

progress has been made in the development of satisfactory clinical techniques for using these materials.

Viscosity and Flow of Gases

The viscosity, pressure, temperature, and flow relations for fuel and other

gases which are moved in pipelines are being investigated at the request of

the U. S. Bureau of Mines and other interested organizations. These data

are necessary in designing pipeline installations, in judging their efficiency,

and in locating defects in lines now in operation.

4. Heat and Power

To provide a fundamental basis for precise measurements of heat and

power, the Bureau has established and maintains a scale of temperature

from the lowest obtainable to the highest temperatures of incandescent

bodies and flames. Instruments are certified for the measurement of temperatures in this range on the International and Kelvin scales. From the

measurement of temperature alone, the work broadens to include the

determination of quantities of heat by calorimetry in temperature regions

extending over a large part of the scale. Coordinate with the calorimetry

is a study of the thermodynamic properties of solids, liquids, and gases. From these basic fields of research, the work branches into engineering

884100—50 13
applications to automotive and aircraft engines. One branch extends into

the fundamentals of combustion, with applications to gas turbines, jet engines, and jet propulsion. Another branch covers lubrication problems

that arise not only in automotive engines but in all mechanical devices.

The Bureau is also responsible for determining and maintaining standards of viscosity and for certifying the viscosities of fluids used for calibrating

viscometers. It maintains standards for the metering and carburetion of

liquid fuels in internal combustion engines, and for the determination of

the octane and cetane numbers of automotive, aviation, and Diesel engine

fuels. Research is conducted to increase the accuracy of these standards

and to develop improved measuring instruments and apparatus. Thermal

properties of pure substances and commercial materials are determined,

upon requests from other Government agencies, either by direct experiment

or by calculation from the fundamental atomic and molecular properties

of the substances, and published data on thermal properties are critically

reviewed and compiled.

Thermometry

On January 1, 1949, the National Bureau of Standards began using the

definitions of the International Temperature Scale of 1948 both in its own research program and in calibrating instruments for other scientific

and industrial purposes. Based on a draft prepared by members of the

Bureau staff, the new scale was adopted at Paris by the Ninth General Conference on Weights and Measures in October 1948, and the official text was approved for publication before the end of the year. This is the first

revision of the International Temperature Scale since its adoption 21 years

ago. The experimental procedures by which the scale is realized are substantially unchanged, but certain refinements, based upon experience, have

been incorporated to make the scale more uniform and reproducible.

The same fixed points, with one slight modification, are specified in the

1948 scale, and the laboratory procedures for obtaining temperatures between fixed points are essentially the same as those previously used. Only

two revisions in the definition of the scale result in appreciable changes in

the numerical values assigned to measured temperatures. One of these is

the change in the value for the silver point from 960.5° to 960.8° C, which

affects temperatures measured with the standard thermocouple. Thus, in

the range between 630° and 1,063° C, numerical values of temperature are higher than on the 1927 scale, the maximum difference being about 0.4

degree near 800° C. Likewise, the adoption of a new value ( 1.438 cm-deg)

for the constant c2 in the radiation formulas changes all temperatures above

the gold point (1,063° C). In the new scale, Planck's radiation formula

is specified instead of Wien's for calculating temperatures above the gold

point as observed with an optical pyrometer. Since Planck's law is consistent with the thermodynamic scale even at high temperatures, this change

14
removes the upper limit to the scale formerly imposed by the use of Wien's

law.

Thermometry at very low temperatures has recently assumed a new

importance because of the great increase in the number of academic,

government, and industrial laboratories that are engaged in basic research

in low-temperature physics. At present, temperatures are usually determined with hydrogen or helium vapor-pressure thermometers. However,

these thermometers cover only limited temperature ranges, leaving a hiatus

between 5° and 10° K, and are entirely unsuitable for many applications,

such as calorimetry. For this reason, the Bureau has undertaken the development of sensitive and stable resistance thermometers for use between

1° and 50° K. The successful conclusion of this project should result in

instruments that could be calibrated on the thermodynamic temperature

scale and used in any laboratory, thus providing an accurate and uniform

low-temperature scale. The principal advances that have so far been made

are the improvement of the stability of a number of alloy thermometers

by a new method of construction, the construction and test of silicon

thermometers of very high sensitivity, and the design of a gas thermometer

to be used for the basic calibration of secondary standards.

Thermodynamics

The determination, critical evaluation, and formulation of data on the

basic thermal properties of gases, liquids, and solids were continued.

Current efforts are concentrated on data requested by other Government

laboratories, which are also needed by industry.

As an example, recent advances in jet propulsion and high-speed flight

have emphasized the importance of more accurate thermal data for gases

and gas mixtures that occur in wind tunnels and jet engines, such as air,

nitrogen, oxygen, carbon dioxide, water vapor, carbon monoxide, hydrogen,

etc. With the cooperation of the National Advisory Committee for Aeronautics, a series of tables of thermal properties of gases is being compiled.

The compilations present such properties as specific heat, enthalpy, entropy,

compressibility factor, density, vapor pressure, sound velocity, viscosity,

thermal conductivity, and Prandtl number. The tables are based both on

published and unpublished data and on calculations and experiments

carried out at the Bureau. Their range extends from low pressures up to 100 atmospheres, and from low temperatures, such as occur in high-speed

wind tunnels, to 3,000° K, a temperature encountered in jet engines.

Approximately 20 such tabulations, each covering one or more properties

of a single gas, are nearly complete.

To obtain data for these tables, the vapor pressure of oxygen was measured

with high accuracy from the triple point (54.363° K) to the critical point

(154.78° K). The specific heat of carbon dioxide was also determined

for several low pressures at 0° C by means of the vapor flow calorimeter

developed at the Bureau. Apparatus is now being constructed for

15
Magnet assembly used by the Bureau's atomic physics laboratory in the determination of the absolute value of the magnetic moment of the proton (p. 19).

measurements of the thermal conductivity of gases at temperatures up to 500° C and pressures up to 100 atmospheres.

Although the thermal properties of gases at very high temperatures (above

1,500° K) are very difficult to measure, they may be calculated by reliable

methods from spectroscopic data. Studies of the spectra of water-vapor

and carbon dioxide and of the general theory of the structure of such

triatomic molecules were pursued in order to increase the accuracy with

which the thermal properties of these gases may be calculated at the high

temperatures of current interest. The calculations will be checked against

experimental values at lower temperatures. In the course of the spectroscopic work, some 5,000 spectral lines were identified and classified in the

absorption of the sun's radiation by the water vapor in the earth's atmosphere. The dissociation of molecular gases into atoms and molecular

fragments also has a considerable effect on the thermal properties at high

temperatures; calculations of these effects were made and are included in

the tabulations.

To provide the Government with necessary engineering data, the

enthalpies of beryllium and sodium were accurately measured between 0°

and 900° C. The specific heat and other thermodynamic properties of

these elements were also derived. Additional basic calorimetric data, obtained for the Office of Rubber Reserve and the Government's synthetic

rubber program, yielded values for the heat of polymerization of butadiene,

of use in the recently developed method of low-temperature polymerization

for making synthetic rubber. Determinations were also made of heats of

copolymerization of butadiene and styrene in a number of commercial and

16
experimental synthetic rubbers, including GR-S. In addition to their industrial importance, these data provide information concerning the basic

structure of high polymers. •

Low-Temperature Physics

The phenomenon of superconductivity is in many respects the most challenging field of research in low-temperature physics. As a consequence of

the complete disappearance of electrical resistance and the appearance of

perfect diamagnetism at temperatures near absolute zero, spectacular effects

are obtained which, when interpreted theoretically, give promise of a basic

insight into some of the fundamental properties of matter.

Studies of superconductivity now under way at the Bureau include several

different lines of investigation. For example, the transition of a conductor

from the superconducting state to the normal state as a function of current

density was determined. Other investigations during the year dealt with

the differences beween the behavior of superconductors at microwave fre- quencies (10 billion cycles per second) and their behavior with direct currents. Whereas the resistance of a superconductor completely disappears

with direct currents, some resistance is still observable at these high fre- quencies. The behavior of this high-frequency resistance as a function of

temperature and with different metals is of great scientific interest. A third

problem concerned the interaction between a magnetic field and the surface

currents which it sets up in a superconductor. The retarding torques

exerted on a superconducting sphere when it is rotated wtih respect to the

applied field were measured. This experiment aids in determining the

forces which act between the superconducting electrons and the lattice of

the metal.

The anomalous properties of liquid helium n are being investigated below

1° K, principally through study of the phenomenon known as "second

sound." Liquid helium, cooled to 2.19° K (the A-point) or lower, acquires

properties so unique that it is often described as a fourth state of matter.

One of these properties is an abnormally high heat conductivity, for the

basic nature of heat propagation undergoes a complete change at the A-point

to a form of wave motion (second sound) which travels with a definite

velocity. This velocity is determined by introducing heat pulses into liquid

helium and measuring the time they require to travel a known distance to a thermometer.

The determination of specific heats, heats of transition, entropy, and free

energy of the elements and compounds in the temperature range 12° to 370° K has long been an active program at the Bureau. During the year,

measurements were made of the specific heat of diphenyl ether from 13°

to 360° K. An important aspect of the calorimetric program is the use of

the calorimeter for the determination of purity. By measuring the triplepoint temperature as a function of the fraction of sample melted in a heat-of17
fusion experiment, impurities as small as a few parts per million can be measured. Purities of a number of compounds were determined, including

normal heptane, isopropyl alcohol, diphenyl ether, and methylcyclohexane.

Normal heptane is now being prepared for use as a calorimetric standard.

A new program of calorimetry at temperatures between 1° and 20° K

was begun. This program will involve determination of the specific heats of

metals, semiconductors, and superconductors to provide basic information on the specific heats of conduction electrons, which are not otherwise obtainable. A calorimeter of a considerably higher potential accuracy than has

been obtained before was designed and is now being constructed for this

investigation.

Gas Turbines and Jet Engines

The advent of gas turbines and jet engines as practical power plants has

given rise to urgent needs for research in new fields and the extension of old

fields to higher temperatures, pressures, and velocities. During the year

important contributions were made to the solution of problems concerned

with combustion, control of the fuel supply, and the measurement of temperature, composition, and thermal properties of exhaust gases. While activities in these fields were carried on at the request of the military services, the

results also possess great utility for peacetime applications of gas turbines.

Facilities for operating turbojet and ram-jet combustors were improved

and expanded, permitting studies at 2,000° F of instruments in gas streams

having velocities of 1,800 feet per second. Classified research was done on

the evaluation of commercial combustors and their constituent parts and

on the determination of factors basic to burner design. Since flame speed

and temperature are of prime importance in burners of this type, apparatus was built for measuring these characteristics under those conditions of temperature and pressure which prevail in operating engines.

In the field of jet fuels, 24 pure hydrocarbons were synthesized, and the

physical properties of each were accurately determined. Complementing

previous work on 57 aviation gasolines, the heats of combustion of 32 samples

of jet fuel produced under a tentative specification were determined by

precise calorimetry. A single linear equation was developed by means of

which the heat of combustion of each of the gasolines and each of the jet

fuels can be calculated, within a few tenths of 1 percent, from the density

and the aniline point. With this equation, the heats of combustion of other

hydrocarbon fuels having similar properties can be computed from simple

measurements without recourse to the difficult technique of calorimetry.

In addition to normal calibrations of experimental temperature-sensing

instruments, measurements were made of heat loss by radiation, rate of

response, the effects of gas velocity, and ability to withstand corrosion in

streams of exhaust gas. A special thermocouple consisting essentially of

short lengths of iridium and iridium-rhodium alloy wires with a cooled

18
support was developed, calibrated, and found to have considerable promise

for applications in gases at temperatures up to 3,500° F. In the metering of fuels, the sensitivity of flowmeters of the Rotameter

type to the density and viscosity of the fluid was reduced markedly by proper

attention to float design. A rapid and safe method was also developed for

flow-testing spray nozzles and some of their constituent parts with air. .

5. Atomic and Radiation Physics

Recent advances in atomic and molecular physics have made necessary

new techniques, instruments, standards of measurement, safety provisions

for workers and consumers, standard samples for calibration purposes, and

methods of testing and evaluation in this rapidly expanding field. The

Bureau is now engaged in a broad program of fundamental research and

standardization dealing with atomic and molecular spectra, radiometry,

physical electronics, electron optics, mass spectrometry, X-rays, radioactivity,

and atomic and nuclear constants. A portion of the work specifically directed toward the atomic energy program is supported by the Atomic Energy Commission. Much of the remainder is in closely related lines of

research and is carefully coordinated to avoid duplication of effort.

Magnetic Moment of the Proton

The gyromagnetic ratio of the proton was measured precisely in absolute

units by the method of nuclear resonance absorption in a magnetic field. The new value,

y = 2.6752 ±0.0002

radiam

gauss sec

is considerably more accurate than any reported previously. All previous

measurements approaching this precision have been made in terms of the

relative values of other physical constants and not by direct measurements.

Because of the importance of the gyromagnetic ratio as a fundamental

nuclear constant, refinement in its measurement leads to a more precise

knowledge of other important atomic constants. Two of these, the magnetic moment of the proton and the charge-to-mass ratio of the electron,

are, as a result, now known with better precision.

The magnetic moment of the proton calculated from this measurement is 1.4102 ±0.0005 dyne-cm/gauss. This value now has essentially the same

accuracy as the Planck constant h, winch must be used in the calculation,

and represents the first precise determination of the proton moment in absolute units. The charge-to-mass ratio of the electron, e/m, evaluated in

terms of measurements by others of electronic and nuclear g factors, is e/m= 1.75878 ± 0.000 1 6 X 107

. The determination of the gyromagnetic ratio differs by a small but significant amount from previous measurements by less direct atomic-beam

19
The Bureau will soon make radioactive standards of carbon 14 available in the

form of glass ampoules containing 25 milliliters of a 0.1-molar solution of sodium

carbonate (p. 22).

methods at Columbia University. Careful examination shows that the

difference can be explained by the radiation correction to the electron

moment predicted theoretically by Schwinger. The two measurements

thus combine to give quantitative verification of an important contribution

to the physics of the electron.

The nuclear resonance techniques developed in the course of this work

can be applied to good advantage wherever the strength of a magnetic field

must be closely regulated. The problem of magnetic field regulation

arises widely in the use of scientific apparatus (cyclotrons, mass spectrographs, and beta-ray spectrometers) and in industrial equipment (servomechanisms and electromagnets)

.

The new measurement of the proton's gyromagnetic ratio also provides an accurate secondary standard for magnetic fields. In the past, laboratory measurements involving both magnetic and electric fields have been

limited by the low accuracy of the magnetic measurements. Now the situation is reversed, and magnetic fields can be measured more accurately than

electric fields. This advance will be especially useful in the design and

development of scientific and industrial apparatus employing magnetic

fields where it is important to know accurately the spatial distribution in

the field.

Spectra of Fission Products

When uranium atoms of mass 235 are split, the fission products contain

more than 30 atomic species, including two types of elements that have

20
never been found in nature. Milligram quantities of the two artificial

elements, now known as technetium 43 and prometheum 61, have been

separated from fission products by the Oak Ridge National Laboratory and

loaned to the National Bureau of Standards for spectroscopic study re- quested by the Atomic Energy Commission. Spectroscopic data are experimental evidence from which the electronic structure and energy levels ot

the atom are determined. Thus, such data are important to all scientists

investigating the properties of these elements or engaged in research in

atomic and nuclear physics.

Authoritative descriptions of the optical spectra characterizing these new

elements are being made by exciting them in two or more ways, photographing the spectra, measuring the wavelengths and relative intensities, and

sorting out the lines due to neutral atoms from those belonging- to ionized

atoms. A preliminary description of the first two spectra of technetium is nearing completion; it adds more than 2,000 lines to the data of spectroscopy.

The stronger lines of both spectra have been classified as transitions between

identified energy levels which reveal the electron configurations of technetium atoms and ions in normal and excited states. In complexity and

excitation, the spectra of prometheum resemble those of some other rare- earth elements; several thousand new spectral lines have been observed for

this element, but their description has just begun.

Semiconductors

At present, one of the most active fields of research in physics is the

study of the semiconductors. This field was greatly stimulated by the wartime development of crystal diodes, which were extensively used in radar

work and are now finding numerous applications in electronic components.

The recent discovery of a crystal triode, the transistor, which may be used as replacement for vacuum tubes in amplifiers, has also aroused interest in

the subject.

A laboratory has been set up at the Bureau for the investigation of three

specific topics relating to semiconductors. One is the determination of

the properties of a semiconductor in the region where electrical conduction changes from electron type to hole type. It is believed that the results

will clarify the phenomena occurring in the transistor.

Another study is concerned with the measurement of the Hall effect and

conductivity. This information is essential for an evaluation of a semiconducting material. Apparatus is being assembled to study the properties of titanium dioxide, which has considerable promise for use in circuit

elements involving semiconductors.

The third investigation is on lattice defects in ionic crystals and semiconductors. These defects have a great influence on conduction properties, and a knowledge of the number of such defects is essential to a complete understanding of the conduction process.

21
Cathode Emission Processes l

The Bureau is making an investigation for the Office of Naval Research

'

of the physics of composite cathodes. Very low-density vapors of atoms of I selected chemical elements are projected upon the cathodes during pulses

of a few millionths of a second. The effect of these pulsed vapors on the

electron emission of the cathode is observed with a very high-speed cathoderay oscilloscope. The manner in which the pulsed atomic material affects

the electron emission can be learned from observation of the number of

microseconds between the arrival of the vapors and the resulting effect on

the emission. Results at present indicate that a very small quantity of

material pulsed onto a cathode will cause significant emission changes.

Radioactivity

The increasing use of artificially produced radioactive isotopes and

nuclear particles in medical treatment, scientific research, and industrial

applications has created a need for standards of the commonly used

isotopes and for more precise and reliable methods of measuring their

radiations. For example, a program of cooperative measurements showed

discrepancies of several hundred percent in the determinations by various

laboratories of amounts of radioactive material in samples of substances

used for medical treatment. After considerable investigation and development work at the Bureau during the past year, a method of calibrating

and distributing standard samples of radioactive iodine and radioactive

phosphorous was finally devised. As a result of this program, the variations in measurement of these two substances were reduced to a few percent.

A similar program for the establishment of a standard for radioactive

carbon (C14

) was essentially completed, and calibrated samples of this

isotope will soon be available for distribution. An important part of this

investigation is the determination of the half-life of C14

, i. e., the time re- quired for a given quantity of the isotope to decay to one-half its original

amount. Results thus far obtained indicate a provisional value of 5,600

years.

Investigations preliminary to the establishment of standards of other

radioactive isotopes are still in progress. In order to calibrate a radioactive standard, it is necessary to know the kinds of radiation emitted by the

isotope, the energies involved, the rates of emission, and the complete disintegration scheme of the radioisotope and of all its decay products.

Hence, considerable time and effort have been devoted during the past

year to studies of beta and gamma emission and the determination of

beta-gamma and gamma-gamma coincidence rates. An example is the

determination of the beta- and gamma-ray spectra of iodine 131. From

these data and from observations on the beta-gamma and gamma-gamma

coincidences, the nature of the disintegration scheme for this isotope was

established. Similar work has been performed for gold 198, showing that

22
it disintegrates by emission of a single beta ray followed by a single gamma

ray. On the basis of this information, it will be possible to prepare calibrated standards of the isotope.

The method of beta-gamma coincidences for the determination of co- incidence rates is generally difficult to apply to radioisotopes decaying by

positron emission because of the disturbing effect of the annihilation

radiation. A method involving the magnetic deflection of the positrons was developed which now permits the use of the coincidence method for

measuring such radioisotopes as sodium 22, used extensively in medical

work.

Protection Against Radiation

The present availability of large quantities of gamma-emitting radioactive materials from atomic piles and the development of commercial models

of high-energy accelerators have made problems of radiation protection

and shielding increasingly important. Exact wall thicknesses and optimum

types of construction for protection from extremely high-energy radiations

must be obtained. Radioactive materials are now or will soon be available

which will produce the same radiation output, at similar photon energies,

as the million-volt commercial X-ray machines, but at a considerably

smaller cost. These radiations should thus find extensive applications.

In order for their use to be economically feasible, however, it is necessary

to know the minimum protection requirements. Experimental conditions

for such determinations require large laboratory spaces to reduce scattering

from nonessential sources and means for handling large masses of absorbers.

Experiments of this type are now being carried on at the Bureau as part

of a broad program on radiation protection.

At the request of the Atomic Energy Commission, the attenuation of

the gamma rays from cobalt and radium in iron, concrete, and lead was

obtained under broad-beam conditions which closely simulate those found

in practice. Data were obtained for thicknesses up to 2 feet of concrete and

up to 4 inches of iron. From these data an approximate method was worked

out for computing required thicknesses of other barrier materials having an

atomic number below that of iron. Plans are now under way to obtain

similar information with the Bureau's new 50-million-volt betatron.

X-ray Equipment for Medical Use

During the last war, medical X-ray equipment available for use by the

armed forces did not adequately meet their requirements. For example,

unsatisfactory operation of the equipment with gasoline-electric generators was a source of much difficulty. In order to be prepared for any future

emergency, the Department of the Army has now undertaken an extensive

program to develop X-ray equipment specifically for field use. This program is under the technical supervision of the National Bureau of Standards. While the development work is being carried out mainly by X-ray

23
equipment manufacturers under contracts, facilities and trained technical

personnel at the Bureau are being utilized for testing and study of the models

as they are developed, to determine whether they will meet the military

requirements under conditions simulating a wide range of environment and

conditions of use. These studies also include an analysis of the operation

of the equipment with gasoline-electric generators, recommendations for

modification of generator design, and the development of accessory items to provide operational characteristics equivalent to use on the usual commercial power lines. The development work is now about one-half completed, and the results

appear to have considerable significance for the improvement of civilian

X-ray apparatus. For example, the use of gas instead of the usual oil as the

insulating medium in the full-wave generator reduces weight, greatly facilitates replacement of rectifier tubes and repair operations, and permits the

unit to be shipped filled with the gas and ready to operate.

Mass Spectrometry

Many industries—e. g., gas, petroleum, synthetic rubber, chemicals, and

plastics—depend upon the results of gas analyses for control in production

processes. One of the newer analytical instruments, the mass spectrometer,

is proving remarkably useful for the analysis both of gases and of volatile

liquids. This instrument can, in one operation requiring only a few minutes, separate a very complex mixture of gases, and in many instances the

separation provides an immediate identification of each compound in the

mixture. The quantitative determination, however, is accomplished by

mathematical analysis of the spectrometric data, and this may require hours

or days depending on the complexity of the mixture and the method of

computation. In order to eliminate much of this calculation and delay,

the Bureau is cooperating in a program for the systematic compilation of the mass spectra of pure compounds. Spectra of more than 100 pure hydrocarbons were measured and analyzed during the past year for inclusion in

the catalog of mass spectra issued by the American Petroleum Institute.

Further studies of the application of mass spectrometry to research on

molecular structure and to chemical analysis were continued. Techniques

for obtaining quantitative analyses of liquids of low vapor pressure were

investigated. In connection with this work, a micromanometer was developed to measure pressures in the range 10 to 50 microns with a precision

of 1 percent. The instrument is a diaphragm manometer in which displacement of the diaphragm is measured electrically.

An investigation of the thermal dissociation of six polymers used in

common plastics was carried out. The volatile dissociation products were

analyzed by the mass spectrometer, and microanalytical methods were

developed to measure the average molecular weight of the nonvolatile products. The results give insight into the molecular structure of polymers

and the mechanism of dissociation. In addition, the technique of mass24
spectrometer analysis of volatile dissociation products affords a method for

the chemical analysis of polymers.

Properties of Magnetic-Type Electron Lenses

Since the optical properties of magnetic lenses used in electron microscopes and other electron-optical systems are determined by their axial

field distributions, it is desirable to have some means of measuring these

distributions with high accuracy. Apparatus was therefore constructed for

evaluating such fields directly by measuring the force exerted on a specially

wound probe. Although this coil-balance method is in general use for

magnetic measurements, its application to lenses required special adaptation because of the small dimensions involved. Preliminary experiments

with the device have indicated that the fringe fields of magnetic lenses

contain certain irregularities which merit further study.

Electron-Optical Shadow Method

An electron-optical shadow technique was developed, providing a valuable

tool for the quantitative study of electrostatic and magnetic fields of ex- tremely small dimensions. The new method makes use of an electron lens

system to produce a shadow image of a fine wire mesh placed in the path of

the electron beam. From the distortion in the shadow network caused by

deflection of the electrons as they pass through the field under study, accurate

values of field strength are computed. Thus it is possible to investigate

quantitatively fields that have not been susceptible to other methods of investigation, for example, the fringe fields from the small domains of spontaneous magnetization in ferromagnetic materials.

The new development should provide a powerful means for broadening

present knowledge concerning space-charge fields, fields produced by contact

potentials, patch fields in thermionic emission, charge distribution in a gase- ous plasma, waveguide problems, and the basic magnetic properties of

metals. Though similar in some respects to the electron-optical Schlieren

method previously developed at the Bureau, the shadow method is much

better adapted to precise determinations of field intensity.

Perhaps the greatest value of the electron-optical shadow method lies in

its utility for exploring complex electric and magnetic fields of extremely

small dimensions or in which a probe of size greater than the electron would

disturb the field under study. In the past, calculations of the field intensity

at a point have been limited to those special cases in which the geometry

of the field exhibits a high degree of symmetry. The shadow technique now

provides data for accurate calculation of the absolute value of the field

intensity in selected planes about a specimen of any size or shape without

altering or disturbing the field. The method is thus well adapted to investigation of the fundamental

nature of ferromagnetism. Experiments now under way at the Bureau in25
The electron-optical shadow method, a new technique developed at the Bureau,

makes it possible to photograph and study quantitatively electrostatic and magnetic

fields of extremely small dimensions. Above: the method is illustrated by an

analogous experiment in light optics. Below: pattern produced by the field of

a magnetic recording wire. These two photographs were together awarded first prize in the Third Annual Photography-in-Science Salon of the American Association for the Advancement of Science in September 1949.

26
elude a study of the behavior of the fringe fields of the ferromagnetic

domains ; in this work a single crystal of cobalt having very large magnetic

domains is being used. An extension to ferroelectric materials is also con- templated for the purpose of checking the domain theory of these substances;

of particular interest will be a study of the polarization of barium titanate

and other high-dielectric materials which are now being widely used in the

production of small-sized capacitors for radio, radar, and television.

In another application of the shadow method at the Bureau, space-charge

fields in several types of apparatus employing electron beams are being investigated. In this connection, use of the method with a pulsed electron source for the stroboscopic study of fields that vary with time is under study.

It has been suggested that the electron-optical shadow method may also

be of value for the calculation of field intensities within a waveguide. Use

of waveguides as conductors and circuit elements in ultra-high-frequency

radar and communication often leads to arrangements whose geometry is too complicated for expression in any system of mathematical coordinates.

Thus the electronics engineer, having in many cases only an intuitive picture

of the field distribution at junctions and elbows of the guide, must rely on

empirical methods in designing waveguide techniques and equipment. By

the use of suitable auxiliary techniques, it is hoped that the shadow method

may be adapted to the calculation of field intensities in regions of a guide

that are not at present susceptible to analytical treatment.

6. Chemistry

A wide range of fundamental and applied research is carried on in physical, analytical, organic, and inorganic chemistry. Special laboratories are devoted to organic protective coatings, detergents and adsorbents, carbohydrates, metals and alloys, pure substances, electrodeposited coatings, gases, acid-base indicators and pH standards, and hydrocarbons. Highly varied

techniques are used in the analytical work of the several groups; many types

of physico-chemical measurements are made: an entire section, by way of

illustration, is occupied with emission spectroscopy as an analytical tool. Most of the Bureau's "Standard Samples", critical in industrial quality control and in research work throughout the Nation, originate in this division.

Properties of Soaps

Although soaps and other kinds of cleaning materials have been in com- mon use for centuries, there have been no universally accepted quantitative

methods for determining their washing or cleansing power. In an effort

to apply some of the newer scientific techniques to the problem, electronmicroscope and X-ray diffraction studies of soap crystals were carried out

at the Bureau, revealing characteristic features for each type of soap molecule that can be used for its identification. The electron microscope also

indicates the individual soap forms that are present in a mixture, such as a

27
Electron micrographs of soaps and soap mixtures reveal morphological features that serve as excellent guides for a quick characterization of the pure alkali soaps themselves (A) and for the identification of the components of commercial

soap mixtures (B) (p. 27).

commercial soap prepared from mixed fats or oils. This is not always

possible with X-ray observations because of the nature of the diffraction

patterns obtained. In conjunction with physico-chemical measurements

of aqueous soap solutions, these data offer an explanation of the mechanical

process of cleansing and, at the same time, suggest a basis for evaluating

the cleansing power of the different types of soap.

Fundamental Chemistry of Sugars

The manifold role of ammonia and amino compounds in biological and

other branches of organic chemistry makes important the study of the amino

carbohydrate derivatives. The Bureau's development of methods for the

preparation of 1-amino-uronic amides has provided a useful process for

the separation of uronic acids. This work also offers a key to some fundamental problems of organic chemistry, including reactions that may be involved in life processes. It was found that the 1-amino-uronic amides, as well as the simpler glycosyl amines, are sensitive to hydrolysis in a limited

range of acidity, pH 4 to 6. This striking sensitivity is explained by an

equilibrium state involving (1) the glycosyl amine and its cation and (2)

the corresponding imine and its cation. The system seems adequate to account for the sensitivity of certain enzymes in regions of restricted acidity

and for the peculiar role which ammonia plays in some condensation

reactions of aldehydes.

Infrared Spectrometry

In recent years infrared spectrometry has found extensive use as a tool

for the analysis of mixtures of organic compounds and as a means of corre28
lating the properties of substances with the structure of their molecules.

During the year a study of the infrared absorption of sugars and sugar

derivatives was begun as a phase of the continuing work on the fundamental chemistry of carbohydrates. The spectra of 15 sugar derivatives

dissolved in carbon tetrachloride were recorded to identify absorption bands

characteristic of alpha and beta forms as well as those associated with the

ring structures of glucose, mannose, galactose, etc. The spectra of nine

substituted alcohols (3-pentanols) were also recorded to study the association of the hydroxyl groups and to verify the assignment of the band at 2.86

microns attributed to the dimer structure: this work provides information

with which to interpret the structure of the sugars and to elucidate the

structure and mechanism of moisture absorption of cellulose for correlation with physical properties.

Properties of Corn Products

Products derived from corn are the basis of a very large industry in the

United States. Under the Research Associate plan, the Bureau is engaged,

with the Corn Industries Research Foundation, in cooperative research on

those properties of corn products that are fundamental to the industrial

processing of the materials. Among these products dextrose (corn sugar) is of outstanding importance. During this year extensive systematic measure- ments were made of the vapor pressure, boiling points, and heat capacities

of dextrose solutions.

Paints, Varnishes, and Lacquers

It is estimated that the Government spends $100,000,000 annually on

paints and related materials. The cost of applying them is perhaps four

times this figure. The knowledge of paints, varnishes, and lacquers which

has been accumulated at the Bureau through many years of work on these

materials is thus of steadily increasing value to Government agencies in

problems of procurement and utilization. During the year special emphasis was placed on the development and improvement of specifications in this

field to keep abreast of technological changes and the needs of the Government. Thus, in testing for conformance to specifications, priority was

given to samples representing large Government purchases or centralized

Government procurement plans. For the last 6 months of the fiscal year,

40 percent of the paints and 13 percent of the varnishes tested for con- formance to Government specifications were found to be substandard.

This clearly shows that Government procurement of these important commodities is as yet far from satisfactory and that more systematic attention

should be given to its improvement.

Dissociation Constants of Organic Compounds

When certain organic compounds are dissolved in water, they dissociate

to give acid or alkaline reactions that are important in many fields, includSS4100—50 3 29
ing biology and medicine. Several well-known methods are available for

the determination of the physico-chemical equilibria if the dissociation proceeds in a simple manner. However, for systems in which two or more

dissociations are involved, the procedures are more complicated, especially

if the constants have nearly the same values.

Many organic substances which are colorless in solution have broad, intense absorption bands in the ultraviolet region of the spectrum. The

bands may shift considerably in position and intensity if the acidity or alkalinity of the solution is changed. On the basis of this phenomenon, a method of calculating two closely overlapping dissociation constants of

organic compounds from spectrophotometry data was developed. While

extensive experimental observations and subsequent calculations are re- quired to determine the amounts of the several dissociation products in

solution, the method is especially useful for materials that do not dissolve

readily and for solutions of low concentrations where other procedures give

low precision or fail.

Hydrocarbons

The work on hydrocarbons, performed largely in cooperation with the

American Petroleum Institute through its Research Projects 6 and 44, has

continued to produce results of fundamental importance for the industrial

and scientific laboratories of the petroleum, chemical, and rubber industries. During the year, a new theoretical analysis of the fractionating process of adsorption was completed; the number of individual hydrocarbons

isolated from one representative crude petroleum was increased to 91;

reports were completed on precision measurements of the simple physical

properties of 60 highly purified hydrocarbons of the API-NBS series; purification and determination of purity were completed for 25 hydrocarbon

compounds; determinations of the purity of 3 organic sulfur compounds

were completed; and arrangements were made for commercial production

of a full-scale laboratory model of the rotary concentric-tube distilling column previously developed at the Bureau.

The tables of selected values of physical and thermodynamic properties

of hydrocarbons, which now contain 722 pages and cover 456 hydrocarbons

and related compounds, are being used by nearly 1,500 laboratories in this'

country and abroad. The catalogs of spectral data, which are largely used

by industry for analytical purposes, now include the following: Infrared

spectra, 879 pages, 419 compounds; ultraviolet spectra, 293 pages, 181

compounds; Raman spectra, 159 pages, 155 compounds; mass spectra, 364

pages, 277 compounds. Approximately two-thirds of the compounds are hydrocarbons and one-third are other types of compounds.

Thermochemistry

Experimental determination was completed of the heats of formation

of several important substances, including diborane, pentaborane, cyclo30
octatetraene, and the five isomeric dimethylcyclopentanes. Work is in

progress on a number of alcohols and the C4 hydrocarbons. A total of

568 pages of tables of Selected Values of Chemical Thermodynamic Properties have been issued to date in loose-leaf form. The distribution of these

data covers 1,580 laboratories, of which 140 are abroad. These tables bring

together all available data in a form readily accessible to the engineer,

chemist, and physicist in scientific and industrial research. They provide

accurate values of the thermodynamic properties needed to calculate the

optimum conditions for chemical manufacturing processes.

Gas-Burning Appliances

A large amount of work was done in an effort to develop expressions

which will show the effects of changes in composition of fuel gases on the

operation, and particularly on the safety, of gas-burning appliances. The

subject is one of great importance when a change in the sources of gas

supply to a community, or the supplementing of a supply during peak

demands, is under consideration. Tentative formulas have been developed,

but they require further study and comparison with the large amount of

reported experimental data before they can be used with complete confidence. The elements of design which affect the performance of natural

gas burners of the types commonly used in laboratories were studied

experimentally. Most of the burners made commercially for the purpose

have been tested. Conferences were held with the manufacturers which,

it is believed, will result in considerable improvement in the burners offered

for sale. A Federal specification for use in the purchase of burners was

also prepared.

Electrodeposition

Research in electrodeposition was mainly concerned with the application

of electroplating to military problems. However, several projects of general

interest were completed or under way during the year. For example, the

physical properties of nickel deposited under a wide variety of conditions were measured in cooperation with the American Electroplaters' Society.

The results, now being assembled for publication, will facilitate the electroforming of nickel for specified purposes. Conditions were also determined

for the codeposition of as much as 15 percent of phosphorus with nickel and

cobalt. The deposits are relatively brittle, but they are hard and can be

further hardened by heat treatment. This property may prove useful in

special applications.

By use of the radioactive isotope, chromium 51, it was shown that in the

chromic acid bath chromium is deposited directly from the sexavalent state and not, as often assumed, through the trivalent chromium that is also

normally present. The results throw light on the mechanism of electrodeposition and also point the way to other researches with tracer elements.

Investigations were begun on the deposition of metals such as tungsten,

31
Left: radioactive tracer techniques were used to study the mechanism of chromium

plating. A Geiger counter is being placed inside a tube upon which radioactive

chromium 51 has been deposited (p. 31). Right: the chemical composition of a sample material is determined in the Bureau's spectrochemistry laboratory.

molybdenum, titanium, and zirconium from aqueous solutions at temperatures up to 300° C and from fused electrolytes and nonaqueous solutions.

Redetermination of the Faraday

The present accepted value of the faraday was determined at the Bureau

over 30 years ago. The method used was based on the electrolytic deposition of silver, an element whose atomic weight had been very accurately

determined. In an electrochemical investigation now being conducted for

redetermination of the faraday, emphasis is being placed on new methods

of approach as well as on the checking of older methods. Anodic and

cathodic reactions have been studied, and substances other than silver

have been utilized. The values so far obtained do not differ greatly from

the present one, but it is believed that the final' result will have a higher

order of accuracy. In the cathodic reactions very accurate methods of

determining the ever-present inclusions must be developed. This work

should also result in valuable information on electrochemical equivalents,

chemical standards, and atomic weights.

Spectrochemical Analysis

In the last 25 years the development of spectrochemical analysis has

greatly aided the analytical chemist in coping with the growing complexity

of industrial materials, especially in the fields of metals and mineral products. Since the first crude beginnings in the twenties, the technique has

increased steadily in accuracy and diversity of use. During the past year emphasis was placed on the preparation of spectro^

graphic standard samples and on improvements in methods of exciting

32
spectra and recording them. Five tin standards intended for the analysis

of pure tin in industry were prepared by casting molten tin, with known

additions of impurities, into bars which were then made into one-fourth-inch

rods. Spectrographic tests showed that the rods were highly homogeneous

with respect to the distribution of the 10 added constituents. The actual

composition of these standards, which must be arrived at by conventional

chemical analysis in addition to spectrochemical comparisons, is now being

determined by a group of cooperating Government and industrial

laboratories.

To improve speed and precision in testing spectrographic standard samples for uniformity, a direct-reading electronic spectrometer was installed

and applied to the examination of two steel standards. The instrument

provides an analysis of a sample for both major and minor constituents in

5 minutes. A high-voltage spark unit for the excitation of spectra was

designed and built in order to provide higher precision in spectroscopic

analysis, particularly of complex steels.

Pure Substances

Several special-purpose materials of exceptional purity were prepared.

These include a substance intended to serve as a new thermometric standard and three calorimetric standards which will be issued to a group of laboratories cooperating in a program of refining and standardizing calorimetric

procedures.

The calorimetric standards—normal heptane, benzoic acid, and synthetic

sapphire—were prepared specifically for use in highly accurate measure- ments of heat capacity. The proposed new thermometric standard is diphenyl oxide. Cells containing this substance, whose freezing point is near 27° C, have been found to maintain a temperature constant to a few

ten-thousandths of a degree for as long as 48 hours. Such cells can provide

a means of calibrating platinum resistance thermometers at a temperature

close to 25° G and thus keep them under accurate control in the temperature range where many measurements of physical and chemical properties

are made. Measurements which will determine the exact degree of constancy and reproducibility of the diphenyl oxide cells are still in progress.

An alcohol which freezes near 25° C will also be studied to determine

whether its characteristics are in any way better than those of diphenyl

oxide. When facilities permit, it is planned to issue to the public cells containing one or the other of these substances. They will supplement the

benzoic acid thermometric standard which is now in regular production.

Mercury is a metal of diversified scientific uses, all of which demand a high degree of purity. For many years the Bureau has purified mercury

for the use of its own laboratories and of several other Government agencies.

This year the amount of metal purified was nearly 2,300 pounds, of which

700 pounds was required by one agency. By means of radioactive tracer

33
techniques, a study was made of the rate and degree of removal of basemetal impurities from mercury by treatment with nitric acid. The results

showed that this much-used method of purification, if properly performed, can be regarded as "complete" with respect to all metal impurities other

than gold, silver, and the metals of the platinum group.

Work was also done on the preparation of pure germanium, a metal

whose characteristics as a transistor (semiconductor) are very sensitive to minute amounts of impurities. When sufficiently pure germanium is obtained, it will be possible to study the effect of adding various elements

normally present as impurities as well as other elements which may be

significant.

7. Mechanics

The mechanics of solids, liquids, and gases are the broad topics of research

in this field. In scope the work varies from long-range investigations of basic

mechanical phenomena to short-range studies of the mechanical action

of practical apparatus.

Projects dealing with solids include studies of the propagation of sound

over a wide frequency range through vibration-isolating materials such as rubber and felt; the absorption and transmission of sound in building materials; the piezoelectric coefficients of crystalline materials; the nature of

elastic and plastic yielding in structural elements such as strips and plates

under axial and under twisting loads ; the strength under pulsating loads of

riveted joints such as are used in aircraft ; surveys of strain distribution under

load in complicated engineering structures, such as fabricated columns, box

beams, and bulkhead intersections, to check the "stress analysis" for the design of these structures ; the measurement and computation of the vibration

on model airplanes resulting from the landing impact; and improved techniques for measuring strain, displacement, acceleration, and force.

Work on the mechanics of liquids includes investigations of the propagation of surface waves and of waves at the interface between liquids of

different densities, such as are present in the estuaries of rivers; the flow of

water and air in plumbing systems ; and improved techniques and standards

for the precise measurement and control of pressure over a wide range.

Research on the mechanics of gases is concerned with the nature of the

air flow at the surface of an airfoil; damping screens for smoother air flow

in wind tunnels; the transmission of ultrasonic sound waves through gases

at very low densities; measurement of turbulence at supersonic speeds; development of an "artificial ear" consisting of an acoustic coupler which will

approximate the human ear in its ability to receive sound energy from a

hearing aid; the recording and reproduction of audible sound, largely for

application to the manufacture of talking books for use by the blind; the

application of critical flow phenomena to the design of instruments and

pressure lines; and accurate regulation of the flow and mixture of gases,

34
particularly for maintaining an adequate supply of oxygen to the pilot during

high-altitude flight.

Pfund Sky Compass

In polar regions the magnetic compass loses its value as a direction indicator because of the weakness and directional variability in the horizontal

component of the earth's magnetic field. In addition, a primary handicap

to navigation has been the lack of a direction reference during long twilight

periods when neither the sun nor the stars can be used. Considerable modification of conventional methods of aircraft navigation has therefore been

required in such regions, where magnetic compasses and other existing instruments are inoperative. To meet this need, the National Bureau of

Standards, at the request of the Bureau of Aeronautics, Department of the

Navy, has developed a sky compass which indicates the direction of flight

of an aircraft and can be used in determining its position.

The sky compass is based on the investigations made by the late A. H.

Pfund of Johns Hopkins University and is an outgrowth of his twilight

sextant. It operates on the principle that scattered sky light, particularly

at twilight, is partially polarized in the plane containing the incident ray

from the sun. The sky compass determines the plane of polarization and

hence the direction of the sun. By use of a clock to rotate the sensitive ele- ment of the compass, the instrument is made to indicate continuously the

direction of flight.

Talking Books for the Blind

Talking books are voice recordings of selected literature which, together

with the reproducers for playing them, are supplied to the blind by the

Library of Congress. As the Library has invested several million dollars

in talking books, it recently requested the Bureau to investigate talking book

production techniques in current use and to set up specifications for the

purchase of talking books and reproducers. The work was begun with the

preparation of an interim specification for talking-book phonographs.

Sample reproducers were tested for compliance with these specifications.

The tests showed large variations among manufacturers in such quantities as

tip radius of the playback needle, tone arm force, and loudspeaker response.

In view of the apparent need for standardization in the industry, arrangements have been made with two of the largest suppliers of talking-book

records for a cooperative study of their recording techniques, with the ulti- mate object of developing a standard technique. A concurrent investigation

aims at determination of playback needle dimensions for maximum fidelity

of reproduction. In connection with this work, 17 talking-book phonographs were tested for the Library of Congress. The test results were used

as a basis for purchase of about 8,000 reproducers, costing approximately

$250,000.

35
Left: the Pfund Sky Compass developed by the Bureau for use in polar regions

where the magnetic compass is ineffective for navigation (p. 35). Right: a hotwire anemometer for measurement of air speed is adjusted in the test section of

the Bureau's 4%-foot wind tunnel (p. 37).

Electric Twinning of Quartz

The electric twinning which sometimes occurs in natural quartz renders

it useless for radio and electronic applications. Moreover, detection of

twinning is difficult, requiring first the sawing and then acid-etching of the

quartz. A method of removing electric twinning systematically from raw

quartz would thus be highly desirable. Such a method would make it possible for the reclaimed quartz to be used for radio-frequency oscillators

and filters and would have considerable economic value. In order to throw some light on the twinning phenomenon, the piezoelectric properties

of quartz were measured at high temperatures (near the inversion temperature of quartz) . The results of the measurements show that one of the

piezoelectric constants goes to zero suddenly at the inversion temperature.

The two twinned forms of quartz which are produced on cooling through

inversion will therefore have different energies when loaded mechanically

in the presence of an electric field. This suggests the possibility of eliminating twinning by suitably combined electrical and mechanical loads. Experi- ^

f ments are planned to investigate this possibility.

Sound Transmission Through Walls

The amount of sound transmitted through a homogeneous building wall

is much greater than the amount computed on the assumption that only

the mass of the wall is effective in reducing sound intensity. A recently

developed theory takes into account not only the mass of the wall but also its bending stiffness and internal dissipation of energy. A comprehensive

laboratory investigation of both single walls and double walls (i. e., two ! single walls separated by an airspace) has shown this flexural theory to be

36
capable of predicting the transmission of airborne sound more accurately

than the older theory. However, much theoretical and experimental work

still remains to be done on the transmission through building structures of

sound produced by impacts on floors and walls.

Boundary Layer Investigations

In cooperation with the National Advisory Committee for Aeronautics,

the Bureau is conducting a long-range investigation of air flow next to the

surface of a body about which air is moving or which is itself moving

through the air. The flow near the surface in a thin region known as the

boundary layer has been of vital concern to the aeronautical engineer

almost since the dawn of flight: the phenomena taking place in this layer

determine such factors as the drag of aircraft and the maximum lift of a

wing. Certain of these phenomena, embraced by the term "turbulence,"

are so complex that definite progress has only recently been made in understanding them. Much of this progress is due to the use now being made

of the highly versatile hot-wire anemometer to measure the statistical properties of turbulent motions. In research conducted in the Bureau's wind

tunnels, measurements have been made of the energy of turbulence, the

average dimensions of the air masses, and the shearing stresses produced

by the turbulent motions. The primary objective of these studies was to

reveal the cause of flow separation, which causes the stalling of wings and

the high drag of blunt bodies. While this work contributed new information, it became more and more apparent as new theories were formulated

that the real need was for a clear physical picture of the processes by which

turbulent motions originate and are sustained against the damping action

of viscosity. The complexity of the problem called for as much simplification as possible. These phenomena are therefore now being investigated

along a smooth flat surface placed in a wind tunnel so that the air flows

parallel to the surface. Measurements are being made of the proportions

of the turbulent energy in different wavelengths in order to obtain data on the energy spectrum, which plays a prominent role in modern theories

of turbulence.

Vacuum-Tube Accelerometer

Of basic importance for estimating the inertia forces in structures subject

to impact and vibration are measurements of acceleration as a function of

time. For this purpose a vacuum-tube accelerometer particularly suitable

for use in aircraft and biomechanical research has been developed at the

Bureau. The accelerometer, which has the appearance of an ordinary

radio vacuum tube, has been used extensively by the Bureau in tests of

model aircraft structures and by the Air Force to determine human toler- ances in ejection seat research. It is being manufactured by one of the

makers of radio vacuum tubes and is now commercially available.

37
The advantages of this accelerometer lie in its high natural frequency

and large electrical output—adequate in many cases for use with relatively

simple equipment. The acceleration-sensitive masses are two plates, which

are spring-mounted so that one plate moves toward, and the other plate

away from, a central fixed cathode when the tube is subjected to acceleration. The change in resistance of the electron stream between the plates

and the cathode is proportional to the acceleration and may be recorded

at a remote point.

Capacities of Plumbing Stacks and Drains

The question of how heavily a vertical soil stack of a given diameter can be loaded with drainage from plumbing fixtures in a building is a very

controversial one on which little experimental data are available. Plumbing

codes differ widely in the number of fixtures that they permit to be discharged into a stack of given diameter and in the way in which these

fixtures may be distributed between different floors. A fundamental investigation of this problem, sponsored by the Housing and Home Finance

Agency, is in progress. Studies have been made of the pressure and flow

conditions that exist at the junction of horizontal drains with the stack

when there is flow coming down the stack from the discharge of fixtures at higher levels. These data, together with a theoretical analysis of the conditions at the junction, make it possible to predict what back-pressure will

be exerted on the flow out of the horizontal drain when a given flow is coming down the stack and a given flow going out of the drain. In this

way the practical capacity of the drain can be predicted for any assumed

conditions.

Flow of Stratified Liquids

Sponsored by the Office of the Chief of Engineers, Department of the

Army, a comprehensive program of theoretical and experimental research on the flow of stratified liquids, such as a body of salt water under fresh

water, has been undertaken. An important objective of this work is to develop model laws pertaining to models of rivers, harbors, and canals,

where density currents of this nature are involved. The problem is of

considerable economic importance, since it involves contamination of public

water supplies, as in New Orleans, and of farm lands by intrusion of salt water from estuaries in the Sacramento River and possibly from navigation

canals. Studies of the flow of a heavy salt or sugar solution from a model

lock under the lighter fresh water in a channel have been made in two

geometrically similar flumes, and further tests will be made in a larger

flume now under construction. An investigation of the damping of solitary waves at the interface' of two liquids of different densities has also been

completed.

38
Investigation of Water Waves

A knowledge of the model laws for the formation of surface waves is important in the interpretation of tests of hydraulic models of harbors

designed to determine the effect of surface waves on structures in the harbor.

Experimental studies are under way to investigate the initial fetch required

for wave development, the growth of wave length and height with distance,

and the mechanism of energy transfer from wind to waves. For this purpose a flume 70 feet long is being used. It has a closed cross section and

blowers mounted at both ends to create an artificial wind over the water.

A theoretical study of tidal waves and a theoretical and experimental study of

the absorption and reflection of waves by porous barriers are being made.

8. Organic and Fibrous Materials

The Bureau investigates rubber, plastics, textiles, leathers, and papers

organic materials whose characteristic properties are due to the long, chainlike structure of their molecules. Such compounds are formed in nature

by a process known as polymerization, in which as many as several million

individual molecules may be joined by chemical reaction. The complex

molecular structure of high polymers, combined with their refusal in many

cases to follow the laws of classical physics, has made it very difficult in the

past to obtain definite fundamental knowledge of their properties. In

recent years, however, rapid progress has been made in the theoretical

science of high polymers, and new techniques have been developed for

measuring their properties and studying their reactions. Many of the new

techniques—such as X-ray diffraction, infrared spectroscopy, and electron

miscroscopy—are being utilized by the Bureau to obtain a better understanding of the fundamental properties of high polymers, both natural and

synthetic, and are leading to more adequate methods and equipment for

developing and evaluating commercial products composed of these materials. During the past year, for example, information obtained in studies

of the shape and size of molecules was utilized to incorporate rubber into

sole'leather in such a way as to improve wearing qualities.

New and continuing projects were under way in many branches of highpolymer chemistry and physics and of materials control and testing. In

the field of rubber they included tire and tube evaluation, studies of secondorder transitions and viscoelastic behavior, and analytical procedures for

synthetic and natural elastomers. In textiles they embraced standardization

of fading tests, infrared spectra and gas absorption of cellulose fibers, and

abrasion resistance of fabrics. Investigations in paper technology were

concerned chiefly with the photochemistry of cellulose, vapor barriers for

buildings, papermaking materials and processes, and paper testing methods.

In the work on leather, attention was directed to improvement of hides by

impregnation with resins or rubber and by treatment with fungicides, the

relation of chemical structure to physical properties, and tannage of fur39
In an investigation of the adhesive properties of a wide variety of adhesives

and adherends (p. 40), tensile-adhesion strengths of the adhesive-adherend combinations were determined using dumbbell-shaped specimens and self-alining grips.

Here a metal-tensile adhesion specimen is being positioned in a hydraulic testing

machine.

skins. Projects in plastics included plasticizer-polymer relations, nature of

adhesion, glazing materials, strength properties at high and low temperatures, and aging problems.

Among the investigations completed during the year were those relating

to strain testing of rubber, deterioration of cotton fabrics exposed to the

weather, laboratory and service tests of hand luggage, fire-retardant coatings

for fabric-covered aircraft, thermal decomposition of polymers, and a statistical method for the study and control of test procedures.

Nature of Adhesion

The use of adhesives as a major aid to construction began during World

War II in connection with intensive building programs for aircraft, ships,

temporary housing, and containers. Emphasis in this new development was

placed on synthetic resins rather than the conventional adhesive materials,

such as animal glue, casein, starch, cellulose compounds, and rubber, which

are used in packaging, bookbinding, and other industries. In 1947 approximately 100 million pounds of synthetic resins were used in adhesives, representing about 8 percent of the total resin production.

Fundamental investigations of adhesives and adhesion were conducted at the National Bureau of Standards in cooperation with the National Advisory

Committee for Aeronautics and the Office of Naval Research. Experiments have shown that the strength of an adhesive joint is dependent not

only on the attracting force between the adhesive and the adherend, but also on mechanical factors such as differences in the modulus of elasticity and

40
thermal expansion of the adhesive and adherend. Further studies are under way to obtain a better understanding of the effects of specific attractive forces on bond strengths.

Fire-Retardant Coatings for Aircraft

The highly flammable cellulose-nitrate dope used on airplane fabrics

has been responsible for much loss of life and property by fire. Although

dopes based on cellulose acetate butyrate are much more difficult to ignite

and have a much lower flame velocity, even they are unsatisfactory in a power plant fire, in which flame from burning gasoline or oil may be in

continuous contact with doped fabric for several seconds.

As the result of a joint research program undertaken by the National

Bureau of Standards and the Civil Aeronautics Administration, coatings were developed for fabric-covered aircraft which approximately double the

time interval between ignition of the fabric and its destruction by fire. These findings, based on both laboratory and wind-tunnel burning tests, provide a basis for more effective extinguishment of fires in flight, particularly those arising from power plants in small craft. The fire-retardant

coatings which proved to be most successful include film-forming substances

and pigments which in burning give off large quantities of noncombustible

gases; substances which exclude oxygen by forming an impenetrable protective glaze; and compounds which absorb the heat of the flame through

endothermic changes.

NBS Method for Microsectioning

The application of the electron microscope to many problems has been

seriously hampered by the lack of a rapid, practical method for cutting

extremely thin sections of organic materials. Because of the very slight

penetrating power of the electron beam and the great relative depth of

field involved, specimen structure is difficult to interpret when sections are over a fraction of a micron in thickness. Yet the techniques that have been

available for preparing thin sections are quite elaborate and difficult, re- quiring expensive equipment and producing few usable sections. The

Bureau therefore undertook to develop a rapid, efficient sectioning procedure which could be carried out in routine fashion by an operator without

a great deal of special training. The resulting method, which goes far in

accomplishing this objective, should be of decided advantage for the production of ultra-thin sections of tissues in such fields as cancer and virus

research. The technique is now being applied at the Bureau to the microsectioning of rayon and other fibrous materials as part of a broad program

in the fundamental study of high polymers.

In the new procedure, n-butyl methacrylate is polymerized around the

specimen to produce an optically clear embedding medium having highly

desirable cutting properties. A smooth, continuous advance of the speci41
Electron micrograph of an extremely thin cross section of onion root tip, showing

cell walls and nuclei. The specimen was prepared for study using a new method

recently developed at the Bureau for cutting very thin sections of tissue. This

photograph was awarded third prize in the Third Annual International Photography-in-Science Salon of the American Association for the Advancement of Science

in September 1949. (Total magnification X 3750.)

42
men toward the knife of a slightly modified conventional microtome is then

obtained from the thermal expansion of a metal specimen holder. Thus

sections having integrity of structure and uniform thickness over a relatively

large area may be cut one at a tme. Metallic shadow casting is employed

for enhancing contrast, increasing observable detail, and creating a threedimensional aspect in some of the structures.

Shrinkage of Collagen

The shrinkage of collagen was studied in an effort to learn more about

the fundamental nature of the reactions occurring in the tanning of leather.

Isothermal measurements of the shrinkage of tendon collagen were made

at various temperatures. The results show that shrinkage is a rate process

and not a phenomenon occurring at a fixed temperature. The theory of

absolute reaction rates has been applied to the data to obtain values of heat,

entropy, and free energy of activation. Results so obtained are in good

agreement with corresponding data reported on denaturation of soluble

proteins. Studies on collagen subjected to tannage show that tannages may

be divided roughly into two classes : ( 1 ) cross-linking, with increased heat

of activation, and (2) non-cross-linking, with increased entropy of activation. Chromium compounds, the outstanding class of tanning agents, are found to produce cross-linking, which is presumed to occur between layers

of polypeptide chains. Most tanning agents, on the other hand, are found

to produce no cross-linking.

Impregnation of Sole Leather With Rubber

A process for incorporating rubber into sole leather was developed which

improves the soles and at the same time conserves leather and tanning materials. This process consists of treating vegetable-tanned crust leather

(the unfinished leather from which sole leather is made) with a solution

of highly milled natural rubber in toluene and evaporating the solvent.

The leather is then ready for use without the additional finishing processes

that would otherwise be required. Laboratory tests indicate that the treat- ment improves the wear by as much as 50 percent and greatly increases

resistance to water. The improved wear resistance, in turn, makes it possible to use portions of the hide that are not normally suitable for soles. Arrangements are being made for the pilot plant production of a number

of soles for a service test on Army shoes.

Aging of Plastics and Rubbers

The life of plastics and rubbers in service depend upon complex processes

of chemical degradation, depolymerization, and polymerization. To aid in

predicting and improving their aging qualities, thin films of nylon, synthetic

rubber, and other synthetic plastics and rubbers were exposed to heat, ultraviolet radiation, and various atmospheric conditions. The effects of

catalysts, inhibitors,, and other ingredients on the rate and course of the

43
degradation were also investigated. The volatile products were collected

in some cases and analyzed by means of the mass spectrometer. The untreated and the treated specimens were examined by the following techniques to obtain information regarding the changes in the structure of the

polymer: infrared absorption, ultraviolet absorption, measurement of viscosity of solutions, measurement of dielectric constant and dissipation factor,

photomicrography, X-ray diffraction, electron microscopy, electron diffraction, and treatment with organic liquids. Some of the techniques gave

definite indication of the course and mechanism of break-down.

Refractive Index of Natural Rubber

The well-known method of determining refractive index by the use of a prism and spectrometer was applied for the first time to measurements on

rubber. A paper presented at the International Rubber Technology Conference in London describes the production of transparent rubber prisms

and gives the results of measurements at five different wavelengths. The

values of the index and the change of index with wavelength are found

to be essentially the same as those of hydrocarbons of similar structure but of

much lower molecular weight. It is possible to calculate the thermal ex- pansivity from the refractive index and its rate of change with temperature.

Photochemistry of Cellulose

An investigation of the effect of light on paper is being conducted as one

phase of a continuing study of the preservation of records. The action of the

light has been found to depend on its wavelength and the atmosphere in

which irradiation takes place. Paper irradiated with far ultraviolet (wavelength about 254 millimicrons) is degraded much more in a dry atmosphere

than in the presence of water vapor. Under these conditions oxygen apparently has no effect. However, upon irradiation with near ultraviolet

(wavelength of maximum intensity at about 388 millimicrons), the changes

that occur appear to depend principally on the presence of oxygen, and to a lesser extent on water vapor and the type of fiber from which the paper was made.

In the study of the photochemistry of cellulose, the degree of polymerization and aldehyde content are two important quantities to be measured.

A very simple procedure was worked out for determination of the fluidity

of cellulose dispersions in cuprammonium hydroxide, from which the degree

of polymerization is readily obtained. An extremely sensitive method for

determination of the aldehyde content of cellulose is now being studied,

using sodium chlorite in a slightly acid medium as an oxidizing agent.

Infrared Analysis of Cellulose

An infrared spectrometric method for the quantitative estimation of the

carboxyl content of cellulosic materials was developed. The method involves the application of Beer's law to absorption spectra of suspensions of

44
Very thin sections of tissue having uniform thickness, large area, and undistorted

structure are prepared for electron-microscope study in almost routine fashion

by means of a new technique developed at the Bureau (p. 41). Smooth, continuous

advance of the embedded specimen toward the knife of a Spencer rotary microtome

is provided by thermal expansion of a brass specimen holder (detail at right),

which is clamped in the microtome a short distance in front of the knife blade.

cellulose in mineral oil and the location of the absorption band due to the

carbonyl of the carboxyl. A carboxyl content of less than 0.02 equivalent

per anhydroglucose unit can be detected by this procedure. Moreover,

the sample required is smaller than that used in the chemical methods

commonly employed for the determination of carboxyl in cellulose. With

suitable modification, the new method is expected to be applicable to the

quantitative estimation of certain other groups in cellulose and cellulose

derivatives. It should thus contribute to an improved understanding and

utilization of such important products as cotton, linen, rayon, films, certain

plastics, and paper.

9. MetallurgyResearch and development in physical metallurgy are concerned with the

preparation of metals and their alloys; the conversion of crude metal to useful shapes by forging, rolling, swaging, wire drawing, specialized casting

processes, and powder metallurgy techniques; determination of the properties of metals and the effect of composition, heat treatment, and other

variables on their behavior at high, low, and ordinary temperatures; study

of the effects of applied stress, corrosion, and other factors on the useful

life of metals and of means of combating these effects. Projects completed or in progress during the year include a study of the occurrence and importance of iron as an impurity in magnesium-zirconium

alloys; the use of polarized light to reveal the stages of deformation of

Monel metal ; investigation of the action of boron in promoting the hardenability of steel; laboratory studies of the chemistry of soil corrosion; field

tests of pipe corrosion; marine-atmosphere exposure tests of aluminum and

884100—50 4 45
magnesium alloys used in aircraft; studies of the effect of particle size and

shape, compacting pressures, and sintering temperatures on the properties

of metal parts produced by the methods of powder metallurgy ; investigation

of the effect of certain variables on the determination of particle-size distribution of the subsieve fractions of metal powders; preparation of "pure

iron"; melting and casting of copper-tin alloys in a high vacuum; investigation of the causes of failure of metals in service; a study of the effects of

strain rate and temperature on the creep characteristics of cold-drawn

ingot iron; and development of a gage for measuring the reduction in area

of test specimens during tensile tests at low temperatures.

Corrosion

It has been estimated that the United States has 500,000 miles of pipe

lines, valued at approximately $6,000,000,000, for the transportation of

water, gas, oil, and gasoline and that the annual cost of pipe replacement,

primarily because of corrosion, is about $200,000,000. In an effort to re- duce this yearly loss, the Bureau began in 1922 a program for the study of

the underground corrosion of metals. This program has received the

active cooperation of producers and users of pipe materials and operators

of pipe lines. During the past year, the Bureau's field tests of pipe corrosion in varied locations throughout the United States were continued, and

reports are now being assembled giving the results of 14 years of exposure

of pipe sections made of iron, steel, copper and copper alloys, lead, and

zinc. It has been found that steels with relatively high contents of chromium and nickel are highly resistant to corrosion in many soils. On the

other hand, small additions of copper, nickel, or chromium, although ef- fective in resisting atmospheric exposure, seem to have little, if any, effect

on the resistance of steel to exposure underground. Dezincification of

brasses apparently can be prevented in soils, as in certain other corrosive

media, by the addition of very small amounts of arsenic.

Because of the time required to obtain data on corrosion and cathodic

protection in field tests, efforts are being made to develop laboratory test procedures and equipment which will provide reliable information on the

progress of corrosion in a relatively short time. Measurements of the

potential of pipe specimens with respect to the surrounding soil environment, with and without cathodic protection of the specimens, are being

made for correlation with the resalts of field tests of long duration.

Study of the corrosive effect of & marine atmosphere on aluminum and

magnesium alloy sheet for aircraft use has been in progress since 1925 under

the sponsorship of the Bureau of Aeronautics (Department of the Navy),

the National Advisory Committee for Aeronautics, and the Department of

the Air Force. During the year, expo-sure of 303 panels was completed

and exposure of 157 new panels begun, including samples of a new construction material composed of a honeycomb core of aluminum foil, impregnated paper, and cotton fabric, all coated with aluminum.

46
Other current corrosion studies include determination of the relative

merits of aluminum alloys, aluminized steel, Monel metal, galvanized steel,

and zinc alloy sheets for use on housing exteriors; development and standardization of salt-spray testing equipment; and continuation of tests to determine the life expectancy of pipe materials in service lines of the

Bureau

Melting and Casting of Metals

Techniques were developed to permit the preparation of 5-lb ingots of

the Bureau's "pure iron" without appreciable contamination. The ingots,

which are to be used to study directly the properties of the elemental metal

and its alloys, are of such high purity that accurate determination of the

impurities constitutes a major problem. To meet the need for special

refractories in which to melt this high-purity iron, an improved procedure

for the production of beryllium oxide crucibles by slip casting was

developed.

By melting and casting copper-tin alloys in a high vacuum, the Bureau

developed metal with tensile properties definitely superior to those of the

same metal melted in air and deoxidized by conventional practices.

Additions of less than 0.5 percent of boron to gray cast iron were shown

to have a pronounced effect on the surface hardness and structural characteristics of the iron. Progress was made in the experimental production of

gray cast iron in which the graphite is present in nodular form instead of the

usual flakes. Cast iron with a transverse strength of 160,000 lb per sq in. has been obtained in this way, but the mechanism of nodular development

has not as yet been determined.

Failure of Metals in Service

The failure or fracture of metals by fatigue under alternating or fluctuating stresses occurs in two stages: (1) The development of a tiny crack

or cracks within the metal and (2) the gradual growth of the crack until

the material is so weakened that complete rupture occurs. Current work

in this field at the Bureau is concerned with the first stage of fatigue. It has been found that bending (prestressing) 24S-T aluminum at relatively

low stress materially improves the fatigue strength at higher stress levels. In another phase of the investigation, X-ray diffraction studies showed that

progressive changes in the strained lattice structure occur with increasing

cycles of stress up to fracture. Attempts to correlate these observations

with the origin and progressive development of fatigue cracks are in progress.

A study of the effect of chromium plating in reducing the fatigue limit

of aircraft steels, requested by the Bureau of Aeronautics, Department of

the Navy, was completed. In some instances the fatigue limit of steel was

reduced more than 50 percent by plating the steel with chromium. The

results show that the fatigue limit of plated steel can be improved by proper

47
heat treatment, but no procedure has yet been found to eliminate all effects

of the plating operation.

Studies of failures in welded ship plate were continued, with the support

of the Ship Structures Committee, representing the Army, Navy, Coast

Guard, Maritime Commission, and American Bureau of Shipping. Recent

results confirm previous conclusions that the fractures originate at notches

or sharp changes in section, that the fractures propagate readily in plates

which are notch-sensitive, and that specifications for ship plate should be

revised to include a notch-senstivity factor since all of the cracked plates so

far examined have complied fully with the requirements of current

specifications.

Failed parts from transportation equipment were subjected to careful

investigation to determine possible causes of failure. Parts from 17 air- craft which had failed were examined during the year for the Civil Aeronautics Board, Civl Aeronautics Administration, and Bureau of Aeronautics

(Department of the Navy) . Several of these failures resulted from fatigue

failures of vital parts. Four bus and truck failures were also examined

for the Interstate Commerce Commission, and two failures of ship parts for

the U. S. Coast Guard.

10. Mineral Products

More than 60 individual research projects were under way in the separate

but closely related fields of porcelain, pottery, glass, refractories, enameled

metals, building stone, concreting materials, lime, and gypsum. As these

nonmetallic, inorganic mineral products are very similar in composition

and constitution, fundamental knowledge of their constituents can be

effectively applied to many specific products. To obtain such information,

basic investigations of the chemical composition, constitution, and structure

of the substances which make up these materials were carried out, and

fundamental constants such as thermal expansivities and specific heats of

crystals and glasses were determined. Important studies concerned the

behavior of mineral products under conditions of temperature and pressure

which might be encountered during fabrication or use. Studies of the

resistance of inorganic, nonmetallic structural materials to weathering, cleaning, and other chemical action were also carried out, and the physical and

chemical conditions required to synthesize large inorganic crystals for

electrical and optical purposes were investigated.

Synthetic Mica

The National Bureau of Standards, with the cooperation of the Office of

Naval Research, has been conducting a program of crystal synthesis to determine the basic conditions necessary for the artificial crystallization of

technically useful silicates, such as mica and asbestos, as well as other hightemperature inorganic compounds. Over 75 percent of the strategically im48
portant mica and asbestos are imported. New products and new uses of

these minerals put a greater dependence on foreign sources. Thus, in time

of emergency the production of synthetic minerals having essentially the same properties as the natural minerals may become highly important.

While the United States is the world's largest consumer of mica, it produces normally only 15 to 35 percent of its requirements of sheet mica and

less than 5 percent of its requirements of mica splittings. No other mineral

or substitute has yet been found that has the electrical insulation property

of the natural micas. However, in the past year a synthetic mica having

essentially the same properties as its equivalent natural mica was successfully crystallized at the Bureau. One property that may make the synthetic

mica superior to the natural material is, its ability to withstand much higher

temperatures before it breaks down structurally. The crystallization of

other silicates, especially amphibole and chrysotile asbestos, has also been

actively studied with promising results.

Ceramic Coatings for Jet Engines

A project is under way, sponsored by the National Advisory Committe(

for Aeronautics, for the development of high-temperature coatings to protect metals and alloys used in jet engines against rapid deterioration from

the effects of the hot gases. Coatings containing large percentages of refractory metal powders blended with a ceramic glass have been developed.

When such coatings are matured by heating to a high temperature in an

inert atmosphere, a metallic-type bond forms between the coating and the

base metal. The glass promotes the formation of the metallic bond layer

and also promotes a welding together of the individual metal particles present in the coating mixture. The result is an interlocking metallic structure

that firmly grips the ceramic coating material. A coating of this type applied to cobalt-bonded titanium carbide (a potential turbine-blade material) protected it against oxidation for 200 hours at 1,800° F.

Ceramic Dielectrics

A series of investigations on ceramic dielectrics was initiated by demands

for materials applicable to miniature electronic devices for the Armed

Forces. A direct result of these studies was a program for the fabrication

of ceramic capacitors, sponsored by the Department of the Army. Three

types of miniature capacitors have now been fabricated. Single-plate and

tubular capacitors meet the specifications for shape, size, capacitance and

temperature coefficient of capacitance set up by the designers of miniature

equipment. Multiple-plate capacitors, assembled from thin plates of ce- ramic dielectrics, have high capacitance per unit volume. These plates,

0.003 and 0.006 inch thick, were made by a newly developed technique for

dry-pressing and firing thin, flat ceramics. The Bureau's program on

ceramic dielectrics has also resulted in materials applicable to many prob

49
lems in very high voltage, X-rays, instantaneous photography, and other

fields. •

High-Temperature Phase-Equilibrium Studies

Methods employing the techniques of high-temperature phase-equilibrium studies have wide application in the development and improvement

of many commercial processes. Such methods have long been in use for

investigation of composition-stability relationships in the systems involved

in portland cements, porcelains, glasses, glazes, and other ceramic products.

The completed results are ordinarily available in the convenient form of

phase diagrams which contain the essential information. In this work it is necessary to trace the compositions of curves or surfaces separating different primary-phase regions or defining other thermal relationships in the

systems. Graphic methods of representation become difficult when the

number of components exceeds three, and impossible when that number

exceeds four. An analytic method, making use of parametric equations, was therefore developed by the Bureau in cooperation with the Portland

Cement Association. These equations make it possible to trace the desired

compositions in systems of any number of components.

Optical Glass

Investigations are under way to determine the physical and chemical

properties of a large number of glasses of widely varied compositions. A

study of a number of glass-forming systems has led to a better understanding of the nature and constitution of glass. These investigations have also

furnished information that is of immediate value in many fields of glass

technology. For example, studies of the durability of glass have been of

value in designing optical glasses of satisfactory durability in service and

also have been useful in preparing specifications for pharmaceutical and

laboratory glassware. Studies of viscosity, surface tension, and other properties of molten glass have been used in determining schedules for melting

optical glass. The information obtained is also of value in formulating

techniques for various glass compositions in all fields of glasswork.

There has recently been a demand by the Armed Forces for very large

optical elements for use in supersonic wind tunnels, large aerial cameras,

and other applications. Where such elements could not be furnished in

suitable quality by commercial firms, the Bureau has undertaken to supply

them. Since long annealing schedules are required to obtain the necessary

optical homogeneity in these elements, the data previously obtained in the

study of crystallization temperatures and rates were essential for this work.

Durability of Building Stone

To study weathering processes on various types and varieties of stone, an

exposure test wall was constructed at the Bureau. This wall contains more

than 2,000 samples of stone, obtained from all of the States except 1 and

50
from 16 foreign countries. Two types of setting mortar were used, one in

each half of the wall. Although the chief purpose of the wall is the study

of actual weathering in relation to laboratory tests for durability, several

structural features are being investigated. Color permanence and discolorations are being studied, and the value of three types of waterproofing is under investigation. An attempt is also being made to determine whether

the combination of certain types of stones in a structure is detrimental to

lasting qualities.

Flow Table for Cement Testing

The 10-inch flow table is an essential instrument in the testing of portland

and masonry cements. Under earlier specifications for this instrument, the

flow values secured with flow tables in different laboratories often varied

sometimes by as much as 30 percent. As a consequence, cement that would

meet specification requirements in one laboratory might fail in another.

Study of the flow table by the National Bureau of Standards in cooperation

with the American Society for Testing Materials has now resulted in a

far more rigid specification for its construction and mounting. The new

specification has been tentatively accepted by the ASTM and is being

favorably considered for promulgation as a Federal specification. The

Cement Reference Laboratory, which is located at the Bureau and supported jointly by the Bureau and the ASTM, developed a mixture for use

in calibrating the flow tables. The mixture is composed of specially ground

silica sand and an appropriate, readily obtainable mineral oil. It can be

used for many repeated tests, will retain its flow properties for at least a month, and has been successfully employed by cooperating laboratories in

testing their flow tables and in adjusting tables and mountings for more

satisfactory performance.

Vitrified China

Investigations directed toward improvement in strength and wear resistance of vitrified china products are being conducted under the sponsorship of the Vitrified China Association. Effective progress in these studies

has been made possible through development of standardized test machines

at the Bureau. For example, refinements of two machines have resulted in

standardization of tests for impact strength and chippage of chinaware.

A recent development is a machine for accelerated tests of the wearing

qualities of glazes. Glazed plates strike and move over those to be abraded

128 times hourly while food-soil, a hot solution of detergent, and hot

rinsing water are periodically introduced. After 48 hours of testing, the wear of the glaze appears comparable to that after 5 years of actual service.

This machine assists in the evaluation of such factors as composition, fit, and bubble population with respect to glaze durability. Other factors

pertaining to durability were revealed in a survey of plants where glaze

51
preparation was observed, and tests were made on glaze materials and

batches.

Service Testing of Porcelain Enamel

Although the degree to which laboratory tests correlate with service data

is a constantly recurring question in many fields of research, the difficulty of

obtaining the needed information and the diversity of service conditions

make even an approximate answer unavailable for numerous accepted

tests. In the past, the Bureau has been instrumental in the development of

a number of tests for porcelain enamels and enameled articles. Recently it began a study designed to compare the results of these and other laboratory

tests with the service performance of typical enameled articles. Enameled

facilities were installed at a series of public housing projects in geographic

areas selected for the diverse characteristics of their local water supplies.

Inspections were made during the year and will be continued at intervals to observe and record the effects of average home service. The results of these

inspections will be compared with the results of a variety of laboratory tests on specimens duplicating those in service. The data obtained will be used

in selecting those laboratory tests which best predict the resistance of enamels

to deterioration in actual use.

Left: water penetration of leather impregnated with rubber by the Bureau's new

process is tested dynamically by means of a specially designed machine. Right:

the increased durability of the rubber-impregnated leather is shown by a service

test in which the plain leather sole was worn away twice as much as the impregnated one (p. 43).

52
11. Building Technology

In addition to its function as a coordinating agency for the research and

standardization activities at the Bureau relating to building constructions

and equipment, the Bureau's Building Technology Division conducts a large

number of investigative programs in the fields of fire protection, safety codes,

heating, air conditioning, refrigeration, thermal insulation, masonry, reinforced concrete, and bituminous materials. Among the research and development projects completed during the year were those on properties

of concretes containing commercial and experimental types of lightweight

aggregates; fire resistance of walls of lightweight-aggregate masonry units;

fire hazards and draft characteristics of masonry chimneys for houses; temperatures in a test bungalow heated by baseboard convectors ; and the design,

construction, and calibration of apparatus for measuring the thermal con- ductance of composite constructions and of refractory materials.

Subjects of other investigations initiated or continued include weathering

of masonry; application of nondestructive dynamic tests to studies of materials; elastic and strength properties of concretes under dynamic loads;

factors affecting the resistance of reinforced concrete beams to failure by

diagonal tension; ignition temperatures of solids; effectiveness of flameretardant chemicals and coatings; susceptibility of materials to spontaneous

heating; intensity and duration of fires in ship staterooms; equipment for

detecting and extinguishing fires; bituminous vapor barrier materials;

weathering of asphalt coatings containing powdered mineral fillers; air

filters ; heating and cooling equipment for aircraft ; grease filters ; and thermal

conductance of solids, liquids, and building constructions.

Reinforcing Bars for Concrete

With the completion of a preliminary study of the bonding efficiencies

of reinforcing bars for concrete, a second program sponsored by the American

Iron and Steel Institute was begun to develop technical information as a

basis for specifications for reinforcing bars and to obtain engineering design

data for the preparation of codes and specifications for reinforced concrete

structures. The earlier research provided technical information which en- abled manufacturers of reinforcing bars to ascertain which types of deformations not only could be produced economically but also would afford excellent resistance to slipping of the bars when embedded in concrete. The

results showed that the bonding resistance was influenced by several factors,

including the depth of concrete below the bar, bearing area and average

height of the deformations, and the inclination of the bearing face of the

deformations with respect to the longitudinal axis of the bar.

The results of this work are already influencing design practices. Concrete reinforcing bars of improved varieties are now readily obtainable by

reference to specifications of the American Society for Testing Materials,

which are based largely upon the data obtained in these studies; and commit53
tees of the American Concrete Institute are studying the data prior to the

formulation of revisions of the building regulations for reinforced concrete.

General application of the results will lead both to better performance of

reinforced concrete structures and to significant economies in their construction and maintenance.

Heat Transfer in Buildings

Under the sponsorship of the Housing and Home Finance Agency, a new hot-box device was developed to obtain accurate information hitherto

lacking on the heat transmission of wall, floor, and roof constructions

containing air spaces and reflective insulation. This apparatus is specially

designed so that specimens can be readily oriented in any desired position,

thus permitting a more complete analysis of heat transfer through the air

space within. After calibration of the apparatus, a frame construction

containing an accordion-pleated reflective insulation was studied in a horizontal position with heat flowing downward and upward, in a vertical

position with the heat flow horizontal, and finally inclined at 45° with the

heat flowing upward and downward. Satisfactory results were obtained

in all of these initial tests.

Fire Protection

Much of the information obtained in fire protection research is directly

useful to authorities concerned with the development of codes and regulations for the construction and operation of ships, buildings, and similar

structures. During the year, specimens representing 21 types of building

constructions were tested as part of a long-range program to develop

engineering design data. These included load-bearing walls, partitions,

floors, and roofings. Ship constructions subjected to fire tests included two

bulkhead and two deck constructions of aluminum, two steel deck constructions, one stateroom of lightweight hydrous calcium silicate material,

and 14 deck finishing compositions. A study of the effectiveness of various

flame-retardant chemicals and coatings was continued, as was a project

directed toward improved measurement of the susceptibility of materials

to spontaneous heating.

Thermal Conductivity at High Temperature

Apparatus was assembled for use in measuring the thermal conductivity

of porous solids at high temperatures, and extensive research was conducted

to verify the soundness of the design and to obtain quantitative data on

errors of measurement. It was found that both the apparatus and the

techniques developed were admirably suited for measuring the conductivities

of refractory materials, rocks, and high-temperature insulations. The

application of the equipment to granular materials was also made possible

54
by placing the materials in a shallow pan of nichrome. Measurements of

thermal conductivities at mean temperatures from 400° to 1,200° F have

now been made on a number of materials, including solid porcelain,

granular bone chars, a magnesia insulating refractory, and powdered insulating materials.

Bituminous Vapor-Barrier Materials

At the request of the Department of the Navy, the Bureau has undertaken a study of bituminous vapor-barrier materials with a view to the

selection of suitable coating materials to be used in conjunction with dehumidifying apparatus for the dehumidification of large storage warehouses.

It is expected that it will be possible in this way to maintain the interior

of warehouses at humidities low enough so that no special packaging of

expensive equipment will be necessary. Approximately 50 representative

coating materials are now under examination. Tests are mainly of the

physical properties of dried films, with particular emphasis on the moisturevapor permeability of unweathered and weathered films. All moisturevapor permeability tests are made on free films of the coating materials.

Codes and Specifications

As a result of changing practices and the introduction of new materials,

several important safety codes were in process of revision during the year.

Cooperative work on development of recommended design practices for

fire safety in Federal buildings to be erected in the future was carried on

with other Federal agencies at the request of the Federal Fire Council.

Federal practices were subjected to detailed study and group discussion in

order to reach agreement on details of safe design for the wide range of

buildings used by the Federal Government. The recommendations growing out of this work are expected to aid materially in reducing losses in

personnel, records, and property.

In response to numerous requests from local committees, officials, and

government agencies for information on how to put building codes on a sound technical basis, the Bureau revised its publication on the preparation

and revision of building codes. Particular attention is given in this publication to the possibility of code improvement through the utilization of

standards based on the results of laboratory research and on the composite

judgment of experienced and competent specialists in their respective fields. The results of many laboratory investigations at the Bureau provide information of much value to the small home owner who undertakes his own

repairs. Realizing that the usefulness of these results could be greatly

increased by presenting the essential facts in nontechnical language, the

Bureau prepared a publication, entitled Care and Repair of the House, in

which suggestions are presented for keeping a house and its equipment in

good condition and for making repairs when necessary.

55
To study the mechanical properties of metals at low temperatures, a specimen is fully submerged (left) in a bath of liquid air. Changes in specimen diameter

are followed accurately with the Bureau's new reduction-of-area gage (p. 46) as the

specimen is extended to fracture. Right: fracture of a box girder at mid-span

after test by the Bureau at 0° F (p. 34).

12. Applied Mathematics

The National Applied Mathematics Laboratories of the Bureau were

established in recognition of the need for a centralized national computational facility equipped with high-speed automatic machinery, capable of

providing a computing service for other Government agencies and staffed

to undertake further development of electronic computing machinery. In

this area the Bureau engages in basic mathematical research and in addition acts as a service organization, particularly in the fields of engineering

statistics and quality control, for the Armed Forces, other governmental

agencies, and industry. The work is organized in four sections: Institute

for Numerical Analysis (at the University of California, Los Angeles),

Computation Laboratory, Machine Development Laboratory, and Statistical Engineering Laboratory.

Numerical Analysis

Four principal lines of research relating to the numerical integration of

linear and nonlinear second-order partial differential equations were pursued. These were (1) numerical methods in conformal mapping, (2)

ordinary differential equations, (3) probability methods in numerical

analysis, (4) miscellaneous studies in applied mathematics involving the

applications and solutions of differential equations. Differential equations

of this kind arise repeatedly in physics, but definitive studies as to the ap56
propriate way to solve such equations in the general cases have not yet been

made. It is quite possible that, if optimum numerical methods are found

for such problems, they will be applicable to higher-order differential

equations of types which have so far evaded all attempts at solution.

Conformal mapping is a powerful tool for solving boundary value problems for plane regions, and some use of it is made in nearly every branch

of classical applied mathematics. The work done on this subject during

the year consisted largely of exposition and background research. A translation of an important collection of Russian papers on numerical conformal

mapping, entitled "Conformal Representation of Simply and Multiply

Connected Regions," was completed; an extensive bibliography containing

many rare items was compiled; and a symposium on the construction and

applications of conformal maps was held. The bibliography and the proceedings of the symposium will be published by the Bureau.

The most important project relating to ordinary differential equations was the preparation of a monograph on their numerical solution. At the

end of the year about 90 percent of the material for this treatise had been

assembled, and about 20 percent of the final manuscript had been completed.

In connection with the monograph, a number of research studies were carried on relating to techniques for numerical integration of simple systems of

ordinary differential equations. For example, a very general theory of the

remainder terms in all forms of linear approximations was developed, and a new method for the numerical integration of ordinary differential equations was worked out which appears to possess rather outstanding advantages

when applied to certain types of equations. Considerable attention was also

given to the determination of the eigenfunction and eigenvalues of linear

differential equations, and a new method for determining eigenvalues was

developed which seems to be much better than the older methods in the

literature.

Studies of probability methods centered on "stochastic processes" and

their applications. A stochastic process can be described mathematically

by a random variable (that is, a variable whose values follow a probability

distribution) which depends upon time—for example, the numbering of calls entering a telephone switchboard in a given time interval or the turbulence

of a fluid in motion at a given time.

Mathematical Tables

Much of the work in mathematical computation involved the tabulation

of the values of fundamental mathematical functions which are encountered

in a variety of physical and mathematical situations. Preparation of 12

basic mathematical tables was continued from the previous fiscal year, and

two more were initiated during the year under review. The two new ones were a radix table for calculating logarithms to many decimal places and a

table of zero and weight factors of the first 16 Hermite polynomials, which

has important applications in the numerical solution of integral equations.

57
A table of Bessel functions Y (z) and Y1 (z) for complex arguments was

completed and accepted by Columbia University Press for publication.

Tables for X-Ray diffraction analysis were completed and were being made

ready for publication in the NBS Applied Mathematics Series. Tables of

Coulomb wave functions, a table of antilogarithms, a volume of tables relat- ing to the Mathieu function, and a table of the exponential integral for complex arguments were nearing completion at the end of the year.

Statistical Engineering

The program in statistical engineering is concerned with the application

of modern statistical inference to complex engineering experiments and

sampling problems and with the analysis of data arising in physical experiments. As in previous years, the research projects in this field were con- cerned principally with the theory of small samples. This was to be ex- pected, for very small sample sizes must often be used in experimentation in

the physical sciences and in engineering testing. Whereas in previous years

work was limited entirely to the consideration of samples formed from

sequences of independent observations, some attention was directed this year

to the properties of samples built from sequences of serially correlated

observations, and a monograph was prepared on stochastic (random) processes from the viewpoint of mathematical statistics.

13. Electronics

In electronics the Bureau carries on research relating to electronic materials and methods as well as pioneering development work on the frontiers

of applied electronics. New and highly specialized types of electronic circuits and components are developed to meet the particular requirements of

industry and national defense. Much of the work is classified and involves

the development of new ordnance devices for the National Military Establishment; a large part of the remainder consists of projects in basic and

applied electronics conducted primarily for other Government agencies.

During the past year, the work in electronics included investigations of

the fundamental behavior of cathodes and gases in electron tubes; development of testing and evaluation procedures for electron tubes; development

of special-purpose electron tubes; investigations in circuit miniaturization,

embracing printed circuitry as well as the use of subminiature components;

design and development of components for electronic digital computing

machines; and design and development of electronic instrumentation for

remote indication of steam turbine clearances and temperatures, the tele- metering of information on the stresses encountered in parachutes, and the

measurement of air turbulence in wind tunnels.

58
Electron Tubes

Rugged electron tubes are indispensable wherever electronic equipment

is used under severe conditions of vibration, shock, or acceleration. In

airline service, for example, tubes in radio or in blind-landing devices must

withstand the vibration of motors, air bumps, and landing shocks. Because

of the importance of reliable tubes of this type in civilian as well as military

use, a comprehensive tube-ruggedization program was initiated during the

past year. A laboratory was installed containing a variety of vibration and

impact equipment, and suitable test procedures were evolved for testing

tubes under vibration conditions and for examining mechanical resonance

effects. Improvement of tube quality is dependent on a better knowledge of the

properties of materials used as tube components, particularly the electronemitting properties of cathodes. To this end, the emission properties of

oxide-coated cathodes in which an alloy of nickel is used as the base metal

are under investigation, with emphasis on determination of the effect of

slight changes in the composition of the nickel alloy. Studies of the diffusion of magnesium through nickel were made, and a suitable test procedure

for evaluating cathode performance was developed. The latter study has

served to emphasize the strong dependence of cathode performance upon

conditions existing in other parts of the tube and has led to the development

of a test diode which will permit control of these conditions.

Electron tubes filled with a noble gas such as argon, neon, or helium are now widely employed in many kinds of electronic equipment. Since gas

density is independent of temperature, gas tubes have a distinct advantage

over those filled with a metallic vapor such as mercury, where the electrical

characteristics change with the thermal variations in vapor density. On

the other hand, the life of gas-filled tubes is limited by the tendency of the

filler gases to disappear inside the tube during operation. An investigation

of this "clean-up" phenomenon, using a helium-filled tube with a tantalum

electrode, has led to the tentative conclusion that clean-up is the result of

the bombardment of a negative electrode by high-velocity gas ions which

penetrate the surfaces and become permanently trapped. Present work is directed toward demonstrating the reversibility of this effect—i. e., toward

effecting complete recovery of the trapped gas from the cathode.

Electronic Miniaturization and Printed Circuits

In a program of electronic miniaturization, sponsored by the Bureau of

Aeronautics, Department of the Navy, production designs were completed

for three specific units of subminiature electronic equipment adaptable to manufacture by commercial mass-production methods.

The first unit is a high-gain wide-band intermediate-frequency amplifier

of radar type. Final designs and model lot production were completed on

this amplifier, which is only one-fourth the size of the original full-scale

59
Synthetic mica (bottom), with essentially the same properties as natural mica

but able to withstand much higher temperatures, was successfully crystallized at the Bureau (p. 48) by melting a mixture of quartz, magnesite, bauxite, and a

fluorosilicate compound in an electric furnace (upper right) at a temperature of

nearly 1,400° C. Upper left: flakes of the synthetic mica are examined under a microscope for structural defects.

60
assembly but provides the same electrical performance. The unit contains

1 1 tubes and has a total volume, including case, of less than 1 1

l/i cubic

inches. The second unit is electrically equivalent to the amplifier described

above but uses printed circuits to the greatest practical extent. This

emphasis on printed circuits is expected to result in increased production

speed, reduced requirements for skilled labor and critical materials, greater

uniformity of production, and lower cost per unit. Printed circuit techniques were found usable throughout, except for the intermediate-frequency

coupling transformers. ' Two basic novelties were featured in the design : the

printing of circuit components on cylindrical surfaces and the use of multilayer printing.

The third unit is a miniature self-contained battery-powered radio trans- ceiver for use by the Navy in rescues at sea. Design of this unit is very

nearly complete, and an initial model, fully meeting the functional requirements, has been constructed. It has a volume of 46 cubic inches, including

a battery pack to provide 20-hour operation.

The principal advances in printed circuit techniques took place in connection with the subminiature printed intermediate-frequency amplifier.

A rotary printer was designed and built for applying printed circuits on

cylindrical surfaces. Additional experimental work was carried out on

the decalcomania method of applying printed circuits. Resistors for use in

printed circuits, applicable by the silk-screen process, were developed from

formulations based on melamine-alkyd resin combinations with high-pH

carbon blacks and suitable dispersing agents. These resistors have lownoise and low-temperature coefficients over the range —60° to +85° C.

The resistance range from 1,500 ohms to 1 megohm has been covered thus

far. Several formulations were also developed for adhesive-tape resistors

having exceptionally low minimum values and good stability over ambient

temperatures up to 200° C. Operation of components at these temperatures is essential in the most advanced miniature designs because of the

high density of the heat-producing elements, such as electron tubes and

resistors.

Electronic Instrumentation

In the program of electronic instrumentation for use in marine engines,

sponsored by the Bureau of Ships, Department of the Navy, significant

progress was made on several projects. Primary emphasis was directed

toward the development of noncontacting electrical precision indicating

devices to measure clearance between stationary and moving parts at several critical points within the steam chest of marine propulsion turbines.

Because of the more rigid requirements imposed upon propulsion turbines

by modern naval operation, an exact knowledge of clearances within the

turbines under extreme conditions of operation has become necessary.

Instrumentation providing the required performance was achieved by an

application of the electronic micrometer, developed at the National Bureau

S84100—50 5 61
of Standards last year on the same instrument program. Seven different

position indicators were designed for operation at the several positions of

interest inside the turbine and its power-transmission gear. These units

provide the requisite resistance to mechanical shock and vibration and to contact with superheated steam, hot oil, oil splash, and vapor. Two of

these devices have been in use aboard ship throughout engineering-test

cruises, providing new information of importance to the operation of the

Fleet. A large-scale instrument system, including 14 position indicators of

several types, has been designed and is in the process of fabrication and

proof test. During the coming year this system is scheduled for installation

in an experimental marine turbine at the Naval Boiler and Turbine

Laboratory.

Two instruments were developed for measuring the thickness of lubricating oil films in sleeve-type bearings. The first model, having a full-scale

range of 0.006 inch and including cathode-ray oscillographic presentation for

fast response, was completed' and installed in the Engineering Experiment

Station of the Bureau of Ships. On the basis of experimental results obtained with this equipment, a second model was developed, providing a

10-fold increase in sensitivity and considerable reduction in the size of

the electronic micrometer input elements. Laboratory development has

now been completed on a third model instrument which uses a novel type

of null-balance iron-core input element to obtain several improved operating features.

A Diesel crankshaft instrument was designed for simultaneous indication of film thickness and shaft vibration from any two of 14 points of

measurement in the crankshaft bearings. Installation of this equipment at

the Engineering Experiment Station is planned for the coming fiscal year.

Development work was completed on three progressively improved sys- tems for multipoint temperature measurement on a high-speed rotating

system without the use of contacting commutators. Since these systems are primarily adaptable to sensory elements of the resistance thermometer

type, future development will be directed toward the achievement of improved subminiature thermometer elements and methods of mounting

them on the blades of gas turbines in turbo superchargers.

Parachute Telemetering Unit

Under the sponsorship of the Bureau of Aeronautics, Department of the

Navy, a low-cost, expendable unit for telemetering functional data from

a descending parachute to a remote ground station was developed for use

in studies of parachute design.

The project involved the design and construction of measuring equipment, a miniature transmitter and coder, and ground stations to receive the

information. The expendable unit, which will cost less than $300, has

seven information channels and an eighth channel for synchronization. It

62
measures and telemeters to ground such data as rate of descent, stress and

strain in body harness and shroud line, opening shock impact, and parachute oscillation. Design of all components of the parachute-borne units,

as well as the required ground stations, is complete. Initial drop tests have

been made, and full-scale proof tests by the sponsoring agency are projected

for the near future.

Characteristics of Electrocardiographs

At the suggestion of the Veterans' Administration, a study was undertaken to determine the adequacy of commercially available electrocardiographs for recording the electrical signals derived from the beating of the

heart. This program has included three major phases: (1) Determination of the instrument characteristics of commercial electrocardiographs in

order to establish the fidelity with which their recording patterns correspond

to the electrical signals they receive, (2) determination of the true characteristics of the electrical signals developed by representative "normal" and

"abnormal" hearts, and (3) establishment of the significance of distortions imposed upon the true cardiac signal with regard to its usefulness as a

basis for clinical diagnoses.

Phases (1) and (2) have been very nearly completed; phase (3) is scheduled for attention during the coming year. This work is of direct

importance in providing a quantitative basis for specifications to be used

in the Government's procurement of electrocardiographic equipment. It

will also aid scientific research in cardiography by providing an initial step

toward the standardization of electrical characteristics of cardiographic

recorders and the recordings which they provide.

14. Automatic Computing Machines

The Bureau's Applied Mathematics Laboratories and its Electronics

Division are jointly conducting an extensive computer program, undertaken

in cooperation with the Office of Naval Research, the Bureau of the Census,

the Department of the Army, and the Department of the Air Force. This

program involves the research, design, and development work necessary to produce electronic machines that will perform, upon instruction, predetermined sequences of calculation running into the thousands of operations

without the intervention of human operators. The result will be the solution in a few hours of complex problems in atomic physics, ballistics, and

aerodynamics which cannot now be solved except by simplifying assumptions

and thousands of man-days of work. The rapidity with which numerical

data can be handled, classified, and analyzed will also be correspondingly

increased.

These new large-scale electronic computing machines are being eagerly

awaited. However, because of their complexity, their construction is a longrange project. Meanwhile, by scaling down certain features of a larger

63
A specimen prepared frc>m one of the special high-temperature ceramic bodies

developed by the Bureau is shown (left) in position for creep tests (p. 49).

Eighteen-foot distillation columns (right), used in the separation of hydrocarbons

from petroleum at the Bureau, are operated 24 hours a day throughout the

year (p. 30).

machine, such as the high-speed memory, the Bureau expects to assemble

within a reasonably short time a machine capable of solving many of the less complicated problems that continually arise in scientific work. Construction

of this machine has now progressed through the preliminary design and

layout stages. It will be a serial-type computer, with a 1 -megacycle repetition rate, and will use an acoustic delay line type of memory. It will also

have provision for the addition of an electrostatic memory. The new highspeed machine will perform a substantial portion of the computation work

of the Bureau's laboratories, solving many problems until recently considered

impossible of solution. It will also aid in computing machine development

at the Bureau and will provide important training and operational experi- ence for personnel of those agencies that plan to operate the more complex

electronic computers as soon as their construction is complete.

The Department of the Army has arranged for the Bureau to act as consultant and design agent for a large-scale electronic digital computer which

the Army expects to construct for its own use. Much of the general design

experience and component development for the Bureau's computer is directly

related to the detailed design of this larger machine. Both machines will

have the same logical structure, which is based on a serial system using an

acoustic delay line memory.

To meet the urgent computational needs of the aircraft industry and Governmental missile research and testing centers on the West Coast, construction of a modest-scale electronic digital computer has been undertaken at

64
the Bureau's Institute for Numerical Analysis in Los Angeles, Calif., with the

support of the Air Materiel Command. The logical design of the INA

Computer has been completed and laid out in block-diagram form. The

high-speed internal memory, which will be of the electrostatic-storage type,

is in the prototype-testing stage of development. The computer design has

been planned so that an intermediate magnetic-drum memory, of relatively

high-storage capacity, can be readily incorporated into the machine. The

detailed design specifications for the arithmetic and control units are now

complete, and construction of these major components of the computer has

begun.

In addition to the machines under construction for its own use, the Bureau

is acting as the procurement and testing agency for five machines for other

Government agencies. A contract for three of these machines (one each

for the Census Bureau, the Army Map Service, and the Air Comptroller) was let during the year. The contract calls for delivery of the first of these

machines by February 1, 1950, but difficulties encountered in design of the

machine will probably require postponement of this date. A contract for a

fourth machine, supported jointly by the Navy and the Air Force, was let to another contractor with delivery scheduled for July 1, 1951. The contract for the fifth machine, which is for the Office of Air Research, is in the

negotiation stage.

15. Radio Propagation

The Central Radio Propagation Laboratory of the Bureau is the primary

agency of the United States Government for the coordination and centralization of information on research in radio wave propagation. The laboratory is also assigned responsibility for development and maintenance of the

national primary standards for electric quantities at frequencies above 10

kilocycles per second.

Comprehensive programs of basic and applied research are undertaken

in radio physics and associated geophysical phenomena of the upper atmosphere and the troposphere. Extensive laboratory studies are also under

way dealing with properties of matter at radio and microwave frequencies

and the development of techniques for precise measurement of electric

quantities in this region. In addition to such research activities, the Bureau

does a large amount of advisory and consulting work on radio for other

agencies of the Government such as the National Military Establishment,

the State Department, and the Federal Communications Commission, and

participates in an advisory capacity in international radio conferences.

The work in radio propagation is divided into three branches: The

Ionospheric Research Laboratory, the Systems Research Laboratory, and

the Measurement Standards Laboratory. The Ionospheric Research

Laboratory carries out basic research on the nature of the upper atmosphere

and its ability to reflect radio waves. The Bureau maintains a widely

65
separated network of 14 ionospheric sounding stations extending over the

; American continents and the Pacific area, the largest network operated by

any one government. Seven of these stations are controlled directly; the

other seven are operated in close cooperation with other agencies. Data

supplied by these observatories provide basic material for scientific research

and for determining frequencies to be used in long-distance radio communication. In addition, a radio propagation field station is operated at

Sterling, Va., for performance of special experiments. Because of the

important influence of extraterrestrial effects on ionospheric phenomena,

solar and cosmic phenomena are studied. These include radio waves

emitted by the sun and other celestial bodies, which also afford a new

means for exploration of the universe.

The Systems Research Laboratory applies radio propagation information

to the practical problems involved in such uses of radio as communication,

navigation, and traffic control, with particular consideration to the advantages and limitations of the types of radio systems concerned. It prepares and publishes a monthly series of charts predicting, three months in

advance, the best frequencies for long-distance communication throughout

the world. These charts are based on data collected by the network of

field stations and by agencies of other national governments. It also con- ducts research in propagation at frequencies in the VHF and UHF bands

which are not reflected by the ionosphere. This part of the program was

greatly expanded during the past year because of increasing public demands

for FM and television service, increasing use of the higher frequencies for

air-to-ground work, and the consequent need for allocation of frequencies on an efficient engineering basis.

The Measurement Standards Laboratory conducts research in methods

for measuring electric quantities at radio and microwave frequencies.

Advances of the last few years have carried this work to higher and higher

frequencies, across the border where classical electromagnetic theory and

quantum theory overlap, and have opened up a new field of basic research

in physical science. An important function of this laboratory is the mainte- nance of standards of electric quantities at these frequencies, including time

;md frequency standards which are broadcast continuously from the Bureau's

radio station, WWV, at Beltsville, Md., and from an experimental station,

WWVH, at Maui, T. H.

Atomic Clock

An atomic clock, based on a constant natural frequency associated with

the vibration of the atoms in the ammonia molecule, was developed, providing a new primary standard of frequency and time. Invariant with age

and independent of astronomical observations, the new clock promises to surpass by one or two orders of magnitude the accuracy of the present

primary standard, the rotating earth. This, the first atomic clock ever

built, is controlled by a constant frequency derived from a microwave

66
The atomic clock (top) developed by the Bureau (p. 66) provides a new primary

standard of frequency and time invariant with age. Lower left: drawing of the

ammonia molecule whose microwave absorption line (lower right) provides the

invariant frequency that controls the timekeeping of the clock. The ammonia gas

is maintained in the 30-ft absorption cell wound around the synchronous clock

above the panel.

67
absorption line of ammonia gas and has a time constancy of 1 part in 20

million. Theoretical considerations indicate a potential accuracy of 1 part in a billion or even 10 billion, depending on the type of atomic system

and spectrum line used.

The present crowding of the radio frequency spectrum has imposed severe

limitations, both nationally and internationally, on the expanding use of

radio for industry and communications. The present allocation of radio

channels allows for a drifting of each station's frequency, so that a broad

channel is required if interference with other stations is to be avoided. The

maximum utilization of available space in the radio spectrum depends on

the accuracy with which the frequency of an individual station can be

controlled, especially at the higher frequencies where quartz crystals cannot

be used as frequency controlling elements. These frequencies, used by

radar, television relays, and microwave equipment in general, could be controlled by atomic elements, permitting a more economical assignment of

spectrum space. Such control would also make possible the permanent

establishment of radio channels on such an exact basis that tuning would be

made as automatic as the dialing of a telephone number.

The improvements in frequency and time measurement offered by the

atomic clock are also of fundamental importance in many fields of science.

An absolute time standard will be of special importance in astronomy, where

present time standards leave much to be desired. The atomic clock and

the method represent important tools of research and development in every

technical field where precise measurements of time and frequency are

crucial—for example, in long-range radio navigation systems, in the upper

range of the microwave region where atomic systems can serve as electronic

components, and in basic research in microwave spectroscopy and molecular

structure. The present time and frequency standards are based on astronomical

determinations of the period of rotation of the earth. However, the earth

is very gradually slowing down in response to the forces of tidal friction in

shallow seas. In addition, there are irregular variations—some of them

rather sudden—in the period of rotation, the reasons for which are un- known. These two causes are responsible for changes in mean solar time

and therefore in the frequency of any periodic or vibrating systems measured in terms of such time standards.

In recent years, vibrations of atoms in molecules—or what are more

specifically termed spectrum lines originating in transitions between energy

levels of these atomic systems—have been found in the microwave region of

the radio spectrum. It has been possible to make very precise measure- ments of these lines by radio methods using all-electronic equipment of

unprecedented sensitivity and resolution. When it became evident that

such spectrum lines might eventually provide new primary frequency

standards, the Bureau began seeking a means of utilizing one of these lines to control an oscillator which in turn could be used to drive a clock. Be68
An experimental masonry wall containing over 2,000 specimens of stone has

been erected at the Bureau for studying the weathering of building stone. Forty- seven States and 16 foreign countries are represented. The wall was designed

so that all phases of the weathering process on numerous varieties of stone could

be studied in the one structure.

cause the resulting equipment, the atomic clock, is controlled by the invariable molecular system of ammonia gas, it provides an atomic standard of time

analogous to the Bureau's new atomic standard of length, which is based on the wavelength of green light emitted by a single mercury isotope.

Microwave Standards

A survey was made of errors in measuring impedance with slotted coaxial

lines and standing-wave ratio methods. Techniques were developed, using

the best coaxial lines available in the country, which gave results practically

independent of all instrument errors except those in the line itself. Considerable progress was made on design, test, and procurement of vertical airdielectric slotted lines having known dimensions uniform to 0.1 percent or more. These are to serve as primary standards of impedance and as useful

standards in measuring power attenuation and voltage.

Field-intensity standards were developed for the very-high-frequency band

at intervals of 25 megacycles. Intercomparison of the "standard field" and

"standard antenna" methods of measuring field intensity gave agreement to a few percent.

69
Quartz-crystal frequency standards and associated monitoring equipment

were improved. Such oscillators showed relative constancy within 4 parts

in 10 billion for intervals up to 10 hours. Initial measurements on improved

quartz-crystal units indicated that a tenfold increase in quality factor and

long-interval constancy can be expected.

The theory and design of an electrodynamic radio-frequency ammeter to serve as a primary standard was completed, and correction formulas for

improving accuracy in studying solid dielectrics were derived. A very sensitive microwave instrument was developed to measure and make a continu- ous record of the dielectric constant of matter as a function of time. Not

only is this instrument a basic research tool for investigating phenomena

causing changes in the dielectric constant of matter, but it also can be

applied to the problem of industrial production control.

Ionospheric Research

Because of the pronounced influence of the sun on the state of the upper

atmosphere, extensive investigations were made of various measures of solar

activity, including sunspot numbers, sunspot areas, "plages," and coronal

intensities. Also under way were studies of the intensity of radio waves

generated by the sun. Known as "solar noise," this phenomenon is a possible index of solar activity. For these studies, two solar radiometers were

constructed and placed in continuous daily operation throughout the daylight hours, one operating on 480 megacycles and another on 160 megacycles. An outstanding event of the year was the observation of an

unusually intense outburst of solar noise which was accompanied by a

simultaneous fade-out of all high-frequency radio signals propagated by the

ionosphere and a flare of bright hydrogen light from a group of sunspots.

If all of the solar noise outburst is assumed to come from the suspected

area, then the intensity of radiation from this area during the burst was two

million times the average intensity from the rest of the sun's visible surface.

The variability of the ionosphere was studied at a number of stations by

determining the variance (mean square deviation) of various parameters,

such as the critical frequency and the maximum usable frequency affecting

propagation. Results of these studies were applied by international confer- ence groups in deciding on allocation of frequencies for high-frequency

broadcast services. Future work in this field is being facilitated by direct

transfer of the raw ionospheric data to punch cards for automatic machine

calculation of the necessary statistics. The punch-card techniques will also

permit economical tabulation and publication of the collected data for the

use of scientists in other research organizations.

Short-term fading of vertical-incidence signals, studied by means of instantaneous values of field intensity recorded at 15-second intervals, indicated differences between the ionosphere in the daytime and at night.

During the night adjacent 15-second values were found to be independent

of each other, but during the day pronounced autocorrelation was observed.

70
This was interpreted as due to the smoother characteristics of the equivalent

reflecting surface of the ionosphere during the day.

Observations were made of round-the-world delayed signals at very low

frequency (18 kc) . Measurements of the differences between the times of

arrival of the "direct" and "round-the-world" signals showed clearly that

this frequency is propagated by multiple reflections between the earth and

the lower ionosphere, and not the surface waves over the earth or beneath

the ionosphere as has been supposed by some investigators.

Additional information about the upper atmosphere is being derived from

radio reflections from meteor trails. Data have been obtained which refute

the views previously held by many investigators that meteors are largely

responsible for sporadic-is reflections. An expanded operational program

for the systematic observation of meteor counts on the approximate fre- qencies of 13 and 27 megacycles was begun during the year, and a photographic recording system was completed for the simultaneous counting of

meteors on several frequencies. Because meteors travel through the at- mosphere at velocities about 100 times that of sound, much basic information

in the field of hypersonic physics may be derived from their study.

Tropospheric Propagation

The major factors influencing propagation at microwave frequencies are tropospheric meteorological effects and terrain geometry. A significant

meteorological effect for very short microwaves is attenuation due to rain.

During the year an extensive investigation of the expected magnitude and

occurrence of serious rainfall attenuation over typical microwave relay

paths was completed. These studies have received attention from both

industrial and military groups as a result of the wide expansion of microwave-relay applications.

Experimental measurements were made of the diffraction of microwaves

of 6-cm wavelength over screens of trees obstructing simple paths up to 3

miles long. The complex patterns of the received signal in the shadow re- gion behind these obstacles contain deep minima resulting from interfer- ence between the direct wave and the ground-reflected waves diffracted over the trees. Heretofore, it has been customary to neglect the ground

reflection at microwave frequencies. This investigation demonstrated the

necessity for having adequate clearance over obstacles on microwave relay

paths designed for maximum reliability.

In order to determine the changing meteorological factors at selected

points along the path of observation in field-intensity measurements, a mobile van was equipped with apparatus for measuring pressure, temperature, and

humidity which, may be carried aloft by a wiredsonde balloon. This equipment is of a special lightweight design and includes the latest type of temperature and humidity elements developed at the Bureau. A special temperature and humidity chamber has been designed for field calibration of this

equipment.

71
A theoretical study was made in an attempt to find a mathematically and

physically plausible method for calculating the field strength of a transmitter

in the presence of irregular terrain. For the problem of large irregularities

such as smooth hills, an integral equation was proposed. To support its

use, the integral equation was solved rigorously for two important special

cases : a plane homogeneous earth and a spherical homogeneous earth. In

both these cases the solution of the equation was found to agree essentially

with the approximate solutions found by other more conventional means. The variablity of refractive index with altitude is an important factor

in determining propagation characteristics in the troposphere. A "microwave atmospheric refractometer" was therefore developed to measure instantaneously the index of refraction of the atmosphere over a small volume

of space. This device consists essentially of two microwave resonant cavities, one of which is a standardized reference ; the atmosphere is drawn through

the other cavity, and the difference in the resonant frequencies of the two

cavities is a direct measure of the index of refraction of the atmosphere.

Correlation of the meteorological and refractive index data with radio field- intensity measurement is expected to yield an understanding of the basic

factors influencing tropospheric radio propagation.

16. Testing, Calibration, and Standard Samples

The Bureau's testing and calibration activities are a natural outgrowth

of its custody of the Nation's basic physical standards. In many cases master standards used in industry or by other laboratories must be checked

periodically against these national standards. The Bureau is also responsible for testing many of the materials purchased by the Government to

assure conformance with specifications. In the course of this work, many

new instruments, new methods of measurement, and much technical data on the properties of materials are developed.

During the year, over 380,000 tests and calibrations were performed for

other Federal agencies and laboratories and industries throughout the country. In the same time over 20,500 standard samples were issued by the

Bureau.

Typical of the tests performed by the Bureau for the Federal Government

is the testing of lamps. In the lamp-testing laboratory, 5,731 light bulbs, a sampling of 4,691,018 purchased by the Government this year, were lifetested. Other representative tests of this kind included the certification of

552 commercial standard cells; determination of hypo content in over 1,300

samples of film in order to insure permanency in archival film records; the

sample-testing of 223,478 clinical thermometers for the Veterans Administration, the U. S. Public Health Service, and the U. S. Department of

Agriculture ; and the examination of 2,083 samples of bituminous materials

to provide information for control of the quality of highway surfacings.

72
Left: test bungalow constructed at the Bureau for research in heat transfer phe- nomena in small houses. This bungalow has since been completely enclosed

within an insulated enclosure (right) so that the temperature outside of the house

can be maintained at any temperature condition encountered throughout the

United States.

For many years, all radium preparations sold in the United States have

been tested and certified by the Bureau as no commercial laboratory is equipped to do this work. During the year, 2,317 tests of such materials

principally medical preparations for hospitals and clinics—were made for

the Government and private concerns. The Bureau also maintains the

only X-ray laboratory in this country where calibration of radiation-measuring instruments in terms of roentgens is possible from 10 to 1,400 kv.

Recent developments in atomic energy, providing opportunities for bodily

injury due to excessive radiation, have made this calibration work increasingly important. Approximately 500 radiation-measuring instruments were

tested for the Atomic Energy Commission to determine their calibrations in

roentgens for different photon energies. Because of the urgent need for

these instruments, which are used in personnel protection, they had been

put in use without thorough investigation of their radiation calibration.

Another important service is the measurement of the amount of radon in

breath samples taken from persons working with radium and radiumluminous paint. This is necessary in order to detect ingestion of harmful

amounts of radium in the body and to apply corrective measures before

injury has occurred. The radon content of 729 such samples were determined for a number of Government agencies and commercial firms.

One of the largest testing projects is the cement-testing program, which

is conducted to insure compliance of Government purchases with Federal

specifications. About 7,000,000 barrels of cement were sample-tested during the year. The increase of approximately 2,000,000 barrels over the

previous year was largely due to increased Federal construction. Both

physical and chemical tests were performed on 19,234 samples of portland

cement, comprising 94,081 separate determinations. The tests were carried out at six separate field stations established for this purpose as well as

at the central laboratory in Washington.

73
Closely related to this work is the program of the Cement Reference

Laboratory, which inspects the apparatus and test methods of cement-testing laboratories. This laboratory is located at the Bureau and is jointly

supported by the Government and the American Society for Testing Materials. Field work of the laboratory includes demonstrations and inspections

of test methods and cement-testing apparatus. During the year, 59 cement

laboratories were inspected throughout the country. The Public Roads

Administration contributes to the financial support of the project and

requires that laboratories testing cement for Federal-aid projects must be

inspected regularly by the Reference Laboratory.

Standard. Samples are materials that are certified for chemical composition or for some physical or chemical property, such as heat of combustion,

melting point, or index of refraction. Standard samples of steels control

the quality of the steel industry's output. Primary chemical standards and

metals with certified melting points make possible uniform measurements

of heat and temperature in the same way that standard weights provide

uniformity of measure in buying and selling. Standard pigments define

the colors of paints, and a large variety of hydrocarbons, supplied as single

substances of high purity, calibrate the instruments that control the composition of motor gasolines, aviation fuels, and synthetic rubber. The list of standard samples issued by the Bureau now includes 450 materials, 25

more than last year.

Electricity and Optics

In the electrical field, standards issued and materials tested included

standard resistors, potentiometers, bridges, capacitors, inductors, ammeters,

voltmeters, wattmeters, watt-hour meters, current and voltage transformers,

insulating materials, magnetic test coils, standard samples of magnetic

material, standard cells, and various types of batteries. For example, in

the past year 552 commercial standard cells were certified; several thousand

batteries of various types were also tested.

Optical standards prepared and issued included lamp standards of candlepower, luminous flux, and color; three types of standards for checking trie photometric, wavelength, and reflectance scales of spectrophotometers;

glass standards of transmittance for calibrating oil colorimeters; porcelainenamel or glass standards of reflectance, opacity, and gloss. In addition,

glass standards of chromaticity and luminance were under preparation for

the television industry, and work was still in progress in preparation for

the life-testing of fluorescent lamps. The testing of precision cameras and

photographic lenses continued in large volume, both for Government

agencies and for industry. Other tests involved telescopes, microscopes,

binoculars, surveying instruments, and sight testers; windshields, goggles,

and sunglasses ; and the determination of refractive indices of optical glasses

and synthetic crystals.

74
In photographic technology, over 1,300 samples of film were tested for

hypo content in order to insure permanency in archival film records. Tests were also made of permanent record film, photographic chemicals, developers, and fixers; and a large number of sensitometric tests were carried

out, principally for the Bureau of Federal Supply. A total of 560 microcopy resolution test charts, to be used in testing microcopying camera and

film combinations, were furnished to various agencies.

Metrology

A major responsibility of the Bureau is the maintenance of the Nation's

basic standards of physical measurement. This involves the testing and

calibration of standard measuring apparatus and reference standards for

precise measurement of length, area, angle, mass, volume, density, and

similar quantities throughout the United States. During the year, 135,640

measurement standards were calibrated, certified, and sent out for service

in laboratories, manufacturing plants, and commercial establishments.

Heat and Power

During the fiscal year, 188,335 separate determinations were made. A

total of 3,382 liquid-in-glass laboratory thermometers, 105 resistance

thermometers, and 351 thermocouples were calibrated; 223,478 clinical

thermometers were sample-tested for the Veterans' Administration, U. S. Public Health Service, and the U. S. Department of Agriculture. Tests

and calibrations of specialized thermometers and thermometric devices required, in many cases, special studies and the construction of appropriate

apparatus. Examples were the tests and investigations made for the Air

Materiel Command on experimental thermometers and temperature-control

equipment for use in turbojet engines in high-speed aircraft.

Large quantites of very pure isooctane (2,2,4-trimethylpentane) and

normal heptane were prepared for distribution as the ultimate primary

standards for the octane rating of gasolines throughout the United States.

Six hundred and fifty-seven standard samples of oils were supplied for the

calibration of viscometers. Three hundred and eighty fuels and lubricants,

162 miscellaneous materials^ and 25 oil filters were tested for compliance

with Federal specifications. Seven hundred and forty-seven automotive

spark plugs were tested for various Government agencies. Automobile

gasoline economizers, gum removers, fuel improvers, and radiator antifreeze and antileak compounds were tested for the Federal Trade Commission and the Post Office Department for detection of fraudulent

advertising. Forty-five tests on aircraft electrical network equipment were

conducted for the Bureau of Aeronautics, Department of the Navy. These

included qualification tests of circuit breakers; performance tests on a

variety of experimental switches, relays, circuit breakers, and connectors;

and examinations to determine the causes of service failures. Other devices

75
tested for Government agencies included armored cars, automobile speed

governors, gasoline-dispensing pumps, automotive and aircraft electric

cable, and model engines.

Atomic and Molecular Physics

The increasing use of radioactive isotopes in medical treatment and

scientific research was reflected in the demand for radium D + E standards,

radium gamma-ray standards, radon standards, rock samples, and radioactive cobalt 60. A total of 937 isotope samples were supplied on request.

In addition, 2,317 tests were made on radium preparations sold in this

country, 500 radiation-measuring instruments were tested for the Atomic

Energy Commission, and 729 breath samples of radium workers were

analyzed for radon content.

During the year, 219 analyses (909 determinations) were made in the mass spectrometer. Thirty-three standards of thermal radiant energy were

calibrated and issued. Miscellaneous radiometric tests performed at the

request of various Government agencies included calibrations of ultraviolet

meters; tests to determine the output of germicidal and therapeutic ultraviolet lamps; determinations of spectral response and sensitivities of thermopiles, photoconducting cells, and similar devices; and determinations of

infrared and ultraviolet absorption characteristics of protective eyeglasses,

special plastics, and optical materials.

Chemistry

A large proportion of the samples tested or analyzed by this Division

represented tests for conformance to Government commodity specifications.

Included were about 850 samples of paints and varnishes, about 1,400 metal

and alloy samples, about 1,500 samples for spectrochemical analysis, and

nearly 2,500 raw sugar samples. This last group, which provides a check on the assaying of raw sugar imports, was approximately 20 percent larger

than in the previous year.

As in other years, there was a considerable amount of nonrepetitive test- ing—the examination of special materials for other laboratories and agencies

for purposes of identification, determination of impurities, or evaluation of

quality. The Federal Trade Commission and the Quartermaster Corps

of the Army were the largest users of this service. The analytical work

performed during and since the war for the Manhattan project and the

Atomic Energy Commission was terminated in April 1949, except for work

of an umpire character, which will be continued.

Mechanics

There was again a pronounced increase over the previous fiscal year in

tests made for Government agencies. The number of master beer meters

tested increased from about 200 in 1948 to about 245 in 1949; an accurate

76
Resistance of lightweight-aggregate concretes to freezing and thawing cycles is determined (left) in this specially designed refrigerator at the Bureau. Right: a bearing wall of hollow brick is drawn into place in front of the Bureau's walltesting furnace in preparation for a fire test (p. 54).

calibration of these meters is essential for the correct computation of Federal tax on beer, amounting to about $800 million per year. The number

of elastic calibrating devices tested increased from 180 in 1948 to 221 in

1949; these devices are responsible for the accuracy of tension and compression testing machines and for the weighing of items ranging from airplanes

to cattle. Tension, compression, bending, torsion, and hardness tests were made on about 1,200 specimens submitted by other Government departments, State institutions, and private organizations to determine mechanical

performance and compliance with specifications; the corresponding figure

for 1948 was 700. Tests for compliance with Federal specifications were made on 32 mechanical appliances, such as floor polishers, motion picture

projectors, and numbering machines; vending machines were tested in connection with fraud cases; 50 oxygen regulators and associated apparatus were evaluated for the Bureau of Aeronautics, Department of the Navy;

and 82 pressure gages and barometers were tested for Government agencies

and the public. Barographs carried in 10 international speed, distance,

and altitude trials of aircraft were tested for the National Aeronautic

Association.

Forty airspeed measuring instruments were tested in the Bureau's wind

tunnels at speeds up to 180 miles per hour. These consisted of cup-andpropeller-type anemometers used in meteorological work and pitot tubes, vane anemometers, and thermal-type anemometers for general-purpose

work such as the measurement of air flow in heating and ventilating sys- tems. Eight microphones were calibrated to be used by other laboratories

as secondary standards for the absolute measurement of sound pressure.

884100—50 6 77
The range over which high-pressure manometers can be calibrated is being extended in response to increasing demands from industry for pressure

calibrations above 10,000 lb per sq in. To this end a mercury manometer

is being constructed as a fundamental standard to cover, for the present,

the range up to 30,000 lb per sq in., and a piston gage of improved characteristics for use as a working standard is being designed to go to 100,000

lb per sq in. One-point portable pressure standards are to be set up, based on the change of state of certain substances such as water, at 30,000, 50,000

and 90,000 lb per sq in.

Organic and Fibrous Materials

During the fiscal year, 41,551 separate determinations were made on

13,716 samples of products containing organic and fibrous materials. This

is a substantial increase over the 33,307 determinations made on 9,085

samples the previous year. Products tested included paper, twine, rope,

rubber footwear, pneumatic tires, glue, hospital sheeting, tile flooring, carpets, mail bags, safety helmets, and plastic materials.

Three new standard samples for rubber compounding were established

in addition to the four standard samples established during fiscal year 1948.

Approximately 2,500 packages of these 7 materials, which are used in

synthetic rubber plants for specification testing of production, were sold to the rubber industry during the past year. They are also used in the 13

standard synthetic-rubber formulas developed by a special subcommittee of

ASTM Committee D-ll.

A new lot of standard light-exposure paper was prepared. Booklets containing a supply of unexposed paper as well as a series of specimens exposed

to known amounts of radiant energy in the Bureau's standard lamp were

distributed to over 500 laboratories in the United States and foreign countries to standardize the exposure of their lamps. In a previous survey of

the performance of such lamps, a variation of more than 200 percent in rate

of exposure was found. It is anticipated that the standard light-exposure

paper will enable different laboratories to control light exposure within a range of about 20 percent. The use of this paper for specification testing

requiring light exposure is now being considered.

In connection with the Federal specifications for brushes, 80 master standards were established. They will be kept by the National Bureau of Standards and used to certify working standards for other Government agencies.

These standards in turn will be used for comparison in acceptance testing of

brush purchases.

Metallurgy

A total of 389 items were examined for quality of material and compliance

with specifications. The largest item was 158 fusible plugs for marine

boilers, examined for the U. S. Coast Guard. One hundred seventeen salt- spray tests were made, and 586 items were heat-treated for various Govern78
ment agencies. Two pressure vessels and one plunger made of 18:8 stainless steel were examined for the Geophysical Laboratory to determine the cause of failure. The experimental foundry prepared 1,495 castings of

aluminum alloys, copper alloys, cast iron, lead, tin, and special compositions

for other Government agencies. Seven sets of the eight standard steels were supplied to other laboratories for use as standards in the determination

of oxygen in steel. Miscellaneous services include rolling, forging, swaging,

and wire drawing of metals and metallographic and X-ray diffraction

examinations.

Mineral Products

During the fiscal year, 124,813 separate determinations were made on

32,178 test items. Materials tested included glass, refractories, cement, concrete and concreting materials, soils, lime and gypsum, enameled metals,

building stone, miscellaneous structural materials, and samples of minerals.

By far the largest testing program was that on cement purchased for use on government construction projects.

Building Technology

The testing of building materials, construction, and equipment for con- formance to specifications was an important activity of the Division. Test

specimens included brick, tile, clay and concrete pipe, waterproofing materials, thermal insulation, and prefabricated assemblies of wall, floor, and

roof constructions. In addition, 2,083 samples of bituminous materials were examined to provide information essential for the control of the quality of

highway surfacings.

Photoflash bulbs submitted by the Civil Aeronautics Board were tested

in order to standardize methods of packaging this commodity for safe

air transport. Many items submitted by the U. S. Coast Guard, such as

signal flares, distress signals, and smoke bombs, were type-tested for reliability and for fire safety with a view to certification as lifeboat and emergency equipment. Type tests were also made on numerous items of ships

stores. Performance tests were made on a baseboard convector for home heating

and on a self-contained heater using alcohol as fuel and employing a steam

turbine as a means for driving a ventilating air blower. A sludge solvent and

a soot remover were analyzed, and their probable effectiveness was estimated.

Five drinking-water coolers were tested for compliance with specifications

as a basis for contract award by the Bureau of Federal Supply. The re- sistance to air flow, the efficiency, and the dust-holding capacity of four types

of air filters were determined, and 24 specimens of porous concrete were examined to ascertain whether they are sufficiently permeable for use in the

construction of grain-storage bins. In cooperation with a member of the

American Academy of Allergy, an investigation was made to determine the

79
In addition to working out adequate methods for testing the ruggedness of electron

tubes (p. 59), the Bureau is developing new kinds of rugged tubes. An X-ray

photograph illustrates the essential structural superiority of ruggedized tubes

compare the heavy, rigid arrangement at right with the narrow, weak design

at left.

ability of a dry-type and a glass-fiber throw-away-type air filter to remove

grains of ragweed pollen from air. A program carried on in cooperation with the American Society of Heating and Ventilating Engineers to determine the reliability of thermal conductivity measurements in different laboratories was nearly completed.

Other thermal conductivity measurements included 28 calibration tests of

heat-flow meters for governmental agencies and industrial firms; 31 tests of

the conductivity of concrete samples both dry and after exposure to a constant humidity; 64 tests of insulating materials for Government agencies;

and 18 tests for industrial and university organizations.

Electronics

Various types of electronic equipment and components were tested and

calibrated for other Government agencies. An example is the testing of

electron tubes. Specially designed, highly accurate, and extremely flexible

equipment has been installed for measuring the characteristics of a wide

variety of tubes, ranging in size from subminiature types to large power tubes

and ranging in frequency from direct-current to microwave. Typical of the

tests conducted during the year were ( 1

) determination of the conformance

of tubes to specifications, (2) evaluation of the suitability of tubes for special

circuit applications, (3) examination and evaluation of tubes in electronic

equipment which had failed or deteriorated, (4) measurement of the static curves of vacuum tubes in the positive grid region, ( 5 ) measurement of characteristics of tubes operating under nonstandard conditions, (6) evaluation

of sample tubes which had been subjected to high-impact shocks and to conditions of extreme vibration, and (7) evaluation of foreign-made tubes and

determination of their characteristics.

80
Radio Propagation

Instruments and devices tested included attenuators, cable, coils, diathermy generators, field-intensity meters, an impedance meter, insulating

materials, a phase shifter, printed resistors, quartz-crystal units, radio receivers, radio-frequency voltmeters, slotted lines, and voltage generators.

Standard frequencies and standard time signals were broadcast continuously

from the Bureau's radio station WWV for use in the calibration and test of

frequency and time standards by the armed services, research laboratories,

and various industries. To further the study of proposals for increasing

the service area of these broadcasts, a new experimental standard frequency

station (WWVH) was established on the island of Maui, Territory of

Hawaii. Frequencies on broadcast from both stations were accurate to 2

parts in 100 million. Continuous services from the new station began on November 22, 1948. Numerous reports on reception indicate that simultaneous operation of the two stations has caused no degradation and that

many arctic and Pacific areas are now consistently receiving standard fre- quencies for the first time. The services are widely used by industries such

as mining, shipping, railroads, power, air transportation, communications,

musical instrument manufacturers, and many others.

17. Technical Services and Cooperation

The Bureau's consulting and advisory activities for other Government

agencies arise from the broad scope of its program in the physical sciences

and mathematics, its wide range of facilities, and expert staff. Since other

branches of the Government as well as industry rely on the Bureau for extensive calibration and test work, the Bureau has taken a leading part in the

development of improved methods for testing materials and equipment, in

determining the physical properties and physical constants of an immense

variety of materials, and in the study of technical processes. As a result,

members of the Bureau staff are called upon by Federal agencies to act as consultants in a great number of fields ; where experimental work is required,

the necessary facilities are usually available at the Bureau.

The Bureau provides calibration services not only to the Federal Government but to State and municipal governments, universities, industry and

private laboratories. In addition, the Bureau offers a program of assistance

to State and local departments of weights and measures, coordinating their

efforts and advising them on technical matters. The Bureau also cooperates

extensively with technical and trade groups, on a national basis, where the

interests of the Government are involved. Such cooperation is not only

of value to the Government but provides a means of disseminating the results

of Bureau work to the Nation in a direct fashion.

The National Bureau of Standards is the technical spokesman for the

United States on international agreements relating to the development and

establishment of international scientific standards and the establishment of

81
values for scientific constants. It is thus active in such groups as the

International Union of Chemistry, International Telecommunications Conference, International Commission on Radiological Units, International

Commission on Radiation Protection, International Commission on

Illumination, and International Commission for Uniform Methods of Sugar

Analysis. Another phase of international cooperation involves a program

whereby scientists or diplomatic representatives from other countries are accepted at the Bureau as guest workers or visitors. Both aspects, which are important to the United States in terms of commerce and trade as well as the international policies of Government, are coordinated on the diplomatic

level by the State Department.

Advisory Services

Advisory and consulting services are rendered to all agencies of the Federal

Government, as well as many State and municipal governments. Agencies

assisted during the year included the Departments of the Army, Navy, and

Air Force; State Department; Department of Agriculture; Post Office Department; Atomic Energy Commission; Federal Communications Commission; Civil Aeronautics Board; Federal Trade Commission; Interstate Commerce Commission; Library of Congress; U. S. Capitol; Joint Chiefs of Staff;

Veterans Administration ; National Capital Parks and Planning Commission; American Battle Monuments Commission; National Park Service;

Bureau of Engraving and Printing; Federal Housing Administration; Housing and Home Finance Agency; Joint Committee of Congress on Printing;

U. S. Maritime Commission; Office of Rubber Reserve; Public Roads Administration; Federal Prison Industries; Bureau of the Mint; Customs

Bureau; Army and Navy Munitions Board; Panama Canal; U. S. Tariff

Commission; Office of International Trade; Bureau of Indian Affairs;

U. S. Bureau of Mines ; Social Security Administration ; Bureau of Foreign

and Domestic Commerce; Civil Aeronautics Administration; Bureau of

NBS Electronic Position Indicator. This instrument was designed at the Bureau

to determine the clearance between rotor and stator blades of propulsion turbines

in the USS Coral Sea during actual operating conditions. At left is the channelselector switch and one of the pick-ups; the other pick-up is shown at right.

82
Federal Supply; U. S. Coast Guard; Public Health Service; Public Buildings

Administration.

Continuous and more extensive work is undertaken through various scientific and technical committees. The Bureau is represented on numerous

committees, panels, and commissions of other Government agencies. These

include the Research and Development Board of the National Military

Establishment, the Federal Interdepartmental Safety Council, the Federal

Fire Council, the Interdepartmental Radio Advisory Committee, the National Conference on Weights and Measures, the National Advisory Committee for Aeronautics, the Interdepartmental Committee on Photographic

Papers and Films, the Interdepartmental Screw Thread Committee, the

Interdepartmental Committee on Fire Tests of Cellulose-Nitrate Motion

Picture Film Vaults, the Joint Committee on Unification of Building Codes,

and a number of similar groups.

Federal Specifications

An important phase of the Bureau's work consists in cooperation with the

Federal Specifications Board and other standardizing agencies in the development and improvement of specifications. To avoid duplication of

effort in Government procurement, the Federal Specifications Board compiles and adopts specifications for the purchase of supplies by the Federal

Government. These specifications result in purchase economies by establishing criteria which guarantee quality and by providing an opportunity

for all businesses to compete for Federal trade through the bid system.

Under the chairmanship of the Director of the National Bureau of Standards and in cooperation with the Bureau of Federal Supply, the Board discharges its functions through 76 technical committees. A total of 156 positions on these committees, including 52 chairmanships or other offices, are

filled by specialists of the Bureau's staff. Considerable experimental investigation is carried on at the Bureau in the development of test methods, which

are so often indispensable before a specification can be framed or applied.

Other laboratory studies become necessary in connection with the continual revision of the specifications to keep them abreast of industrial practice and the changing needs of the Government. More than 2,000 Federal

specifications are now in effect.

Mathematical Problems

One of the primary functions of the Bureau's Applied Mathematics Division has been the furnishing of mathematical services to various Federal

agencies. These services consist mainly of ( 1 ) computing services in connection with specific problems in applied mathematics and (2) consultation

services on the applications of mathematical statistics. Typical of the first type of work was the solution of complicated systems

of simultaneous nonlinear equations describing shock waves which follow an

83
explosion. This was done for the Bureau of Ordnance, Department of the

Navy. Tables and graphs of certain functions which facilitated the solution were prepared. The ultimate purpose of the computations was the prediction of the performance of explosives of various chemical composition.

An outstanding example of the application of computing techniques to the science of management is found in a problem now in process of solution

for the Air Comptroller's Office. The object of the problem is to devise

a purely mechanical process which may be used to replace the thousands

of individual human decisions involved in a major management program.

For example, in achieving a given volume of production or in deploying a certain number of troops and equipment at a given date, it is necessary to procure machines, transportation, materials and supplies, spare parts, and

fuel and to provide for the training of operating and supervisory personnel.

The personnel requirements in the levels of activity involved at each step

have hitherto been the subject of a multitude of separate decisions arrived

at by "educated guessing" on the part of different individuals. The present

project aims to develop methods of replacing these decisions by high-speed

mathematical computation. Methods are being tried out using the most

up-to-date computing equipment available, and further methods will be

tested as better and faster computing machines become available in the

future.

The Johns Hopkins University is conducting for the Operational Research

Office, Department of the Army, a study to determine the physiological

effects of exposure to nuclear radiation. The results will be used to set safety limits and dosages to which workers and military personnel may be

exposed. Because of the obvious difficulty of experimenting with human

beings, experimental material obtained from test animals is used. In connection with this work, the Bureau was asked to compute the life ex- pectancies for animals subjected to various dosages of various types of

radiations and to compare them statistically with the normal life ex- pectancies of unexposed animals. Theories regarding ionization in body

tissues caused by radiation were also evaluated numerically at the Bureau,

and the results are compared statistically with experimental results.

Building Technology

The Bureau provided assistance to other Government agencies on a wide

range of technical problems relating to building constructions and equipment and to fire and other hazards to life and property. For example, the

Public Buildings Service requested the National Bureau of Standards to make tests and inspections in connection with the proposed remodeling of

the White House. Members of the Bureau staff installed strain gage points

and made readings to show the nature and extent of movements of the

masonry. Samples of the masonry materials were tested, and the results

of the tests were interpreted for the engineers responsible for the plans for

renovation.

84
Left: special helium-filled arc discharge tube used by the Bureau in a study of the

problem of gas disappearance in electron tubes filled with a noble gas (p. 59).

An automatic ionosphere recorder (right), designed by the National Bureau of

Standards, is used at the Bureau's Belvoir Field Station to gather ionospheric

data which will aid in predicting radio disturbances (p. 70).

Assistance was given to Federal agencies on many problems of heating

and air conditioning. Thus, the Bureau was consulted on the testing of

the heating system for the Lustron house, and recommendations for the

design of the heating system were prepared. Test data and opinions were

furnished to the Quartermaster General on Army field-cooking, refrigerating, and heating equipment and to the Federal Trade Commission on fuel

oil additives and soot removers. Other agencies obtained data and advice

pertaining to the removal of airborne dust and bacteria, apparatus for

heat-transfer measurements, grain dryers, refrigeration systems, and heating

equipment.

Numerous requests were also received for advice on roofing, waterproofing, and related problems. Warehouse roofs at the Quartermaster General

Depot at Columbus, Ohio, were inspected for the Department of the Army

in an attempt to settle a controversy over responsibility for roof repairs where

the roofs were covered by a surety bond. Other requests were of a more

general nature, dealing with such questions as that of suitable roofing materials on structures in Alaska or the acceptability of new roofing, waterproofing, or siding materials under the requirements of the Federal Housing

Administration.

The Bureau continued to cooperate with the Interagency Committee on

the Texas City Disaster, the Interdepartmental Committee on the Storage

of Motion Picture Film, and the Federal Fire Council. Assistance was

rendered in determining the explosive properties of ammonium nitrate and

inert filler at high temperatures. Tests with the motion picture film

85
storage vault were continued, and information thus obtained was made

available to governmental agencies concerned with the storage of nitrate

film.

Organic and Fibrous Materials

Over 50 Federal agencies were assisted in problems pertaining to natural

and synthetic rubbers, textiles, paper, leather, and organic plastics. For

example, the Office of the Quartermaster General sought advice and assist- ance from the Bureau in the retreating and reconditioning of shoes, athletic

equipment, and other leather products. Fungicidal treatments were developed and retreatment procedures were recommended for items now being

salvaged and stored. As a result, about 1,000,000 pairs of shoes will be

retreated this year, and about 90 carloads of mildewed athletic equipment

will be reconditioned and stored. The total savings on these two items is estimated at $5,000,000.

In another instance, the properties of various plastic insect screens in commercial production were evaluated at the request of several Government

agencies to obtain data for a Federal specification for procurement purposes.

Results of laboratory tests at the Bureau and actual behavior in service

showed that screen woven of monofilaments of saran plastic is equal to or su- perior to bronze screen in most applications. Since plastic insect screen

costs about 20 percent less than bronze screen, the use of plastic screen will

result in considerable savings to the Government.

In cooperation with the Federal Housing Administration and the Housing

and Home Finance Agency, a study was made of various materials for water

vapor barriers. With the advent of tighter building constructions for conservation of fuel and the increasing use of air conditioning, effective vapor

barriers are required to prevent condensation of moisture between walls and

in other parts of structures. This study resulted in the establishment

of standards for vapor barriers used in regulations for new housing

construction.

Mineral Products

Requests for technical assistance in the general field of nonmetallic inorganic mineral products came from a number of different agencies. Consultation services were rendered to the National Capital Parks, the Federal

Bureau of Supplies, the Public Buildings Administration, the Panama Canal,

the American Battle Monument Commission, the U. S. Bureau of Mines, the

Army Corps of Engineers, the Federal Power Commission, and the Office of

the Quartermaster General in matters concerning the use, preservation, and

protection of structural stone. Included were such problems as the repair

of the White House, the preservation of battle monuments, and the selection

of grave markers. The state of Virginia was aided in determining the cause

of damaging expansion taking place in the interior partitions of the Virginia

86
State Historical Library. Assistance was given the Army, Navy, Air Force,

National Advisory Committee for Aeronautics, and the Research and Development Board on procurement and specifications for large optical ele- ments for use with wind tunnels and aerial cameras, and on ceramic coatings

for metals for high-temperature installations.

Consultative services for the Atomic Energy Commission took the form of

two classified surveys to provide ceramic information necessary for the

utilization of atomic energy, and consultation with the Geological Survey

concerning the source and characteristics of fissionable raw materials. The

Bureau of Yards and Docks, Department of the Navy, was aided, through

consultation and field examination, in determining the cause and possible

prevention of expansion in concrete dry docks. In addition, the Bureau

actively participated in the work of the Federal Specifications Board in connection with the introduction and revision of specifications on whitewares,

glass, porcelain-enameled tile, photographic graduates, X-ray processing

tanks, and portland cement.

Commodity Standards

The Commodity Standards Division acts as a secretariat for industry and

trade groups desiring quantitative or qualitative standards. Through formulation of Simplified Practice Recommendations for sizes and varieties of

manufactured products, it aids specific industries in the development of

voluntary programs for the elimination of avoidable waste. It also co- operates with organizations of manufacturers, distributors, and consumers

in the development of voluntary Commercial Standards, which encourage

fair competition through the standardization of methods for testing, rating,

certification, and labeling of commodities.

Work of the Division involves collection and analysis of the necessary data

as well as the actual formulation of the standard for acceptance by the

organizations concerned. Much of the data utilized in the preparation of

the standards results from the research and testing activities of the other

divisions of the Bureau.

Twelve Simplified Practice Recommendations were issued during the fiscal

year. Of these, 2 were new while 10 were revised or reissued. The 2 new

recommendations deal with delivery cases for square milk bottles and the

packing, loading, and marking of steel products for overseas shipments.

Eight new Simplified Practice Recommendations are now in process of

development, and 21 are currently undergoing revision.

Sixteen Commercial Standards were issued, of which 10 were revisions

of previous standards. The 6 new standards covered wire rope (exports),

copper naphthenate wood preservative, colors for polystyrene plastics,

ponderosa pine and sugar pine plywood, model forms for girls' apparel, and

sun-glass lenses made of ground and polished plate. Forty-three new Commercial Standards are currently being developed, and 30 others are at present

undergoing revision.

87
The nearly completed National Bureau of Standards Eastern Automatic Computer (p. 63). Central portion of the machine, showing teletype for transmitting

instructors to the computer (above). Input-output and electrostatic memory

circuits (below). A second computer, the NBS Western Automatic Computer,

is under construction at the NBS Institute for Numerical Analysis in Los Angeles.

88
Weights and Measures

While the National Bureau of Standards is the custodian of the Nation's

standards of length and mass, the Congress has left to the control of the individual States the regulation of commercial weighing and measuring devices

and operations. As the Bureau has no regulatory authority over the weights

and measures activities of the States, it functions only in an advisory and

coordinating capacity in this field. The translation of the basic standards of length and mass and of the

derived standards of capacity to the channels of industry and trade is a

matter of great economic importance to the producing, manufacturing,

processing, and distributing agencies in this country and to all purchasers

of commodities. To aid in this work, the Bureau established late in 1947 an Office of Weights and Measures whose over-all function is to promote

the extension, raise the standard of efficiency and coverage, and increase

the degree of uniformity of State weights and measures supervision throughout the United States. ' A definite program of assistance to State and local

departments of weights and measures as well as to business and industry

has been set up and successfully pursued. During the past year recognition of the importance of such work and the demand for assistance and

advice in this field have continued to increase.

A large part of the activity of the Office of Weights and Measures consists

of consultative services rendered through correspondence; through visits

to the office by representatives of Federal agencies, business and manufacturing concerns, and weights and measures officials; and through visits of

members of the office to weights and measures officials in their own jurisdiction. The field of inquiries is broad, embracing the drafting of new legislation; the interpretation of laws, specifications, tolerances, and regulations;

the design of testing equipment; methods of test of commercial equipment;

the reporting of activities in different weights and measures jurisdictions;

problems of and plans for weights and measures administration; planning

and conducting weights and measures conferences; training schools for

State departments; and the like. A major medium of cooperation with weights and measures officials,

manufacturers of weighing and measuring devices, and associated interests

is the National Conference on Weights and Measures. The thirty-fourth

meeting of this organization was held in Washington in May 1949, under

the sponsorship of the National Bureau of Standards. The official registration of 292 included 160 weights and measures officials from 34 States and

the District of Columbia, 109 representatives of business and industry, and

21 persons from Federal agencies.

As secretary of the conference, the Chief of the Bureau's Office of Weights

and Measures is responsible for planning and conducting the meetings.

He is also a member of the Committee on Specifications and Tolerances, one of the more important standing committees of the conference, which is charged with the development of the technical requirements for commercial

89
weighing and measuring devices. The Bureau has been active in the work

of this committee, whose recommendations lead to the technical requirements promulgated by the States. This year the Conference adopted without change the recommendations of the committee for a complete revision

of the handbook entitled Specifications, Tolerances, and Regulations for

Commercial Weighing and Measuring Devices. The revised material is being published as a new handbook, which will be recommended for promulgation by the States as the legal technical requirements for the various

jurisdictions.

Another important standing committee of the conference is the Committee on Weights and Measures Education, which sponsors and encourages

weights and measures education at all levels throughout the United States. The Office of Weights and Measures is represented on this committee by its

assistant chief, who serves as secretary to the committee.

The Chief of the Office of Weights and Measures is also chairman of the

Technical Committee on Weighing and Measuring Pevices of the Federal

Specifications Board, which has been active during the year in developing

specifications for scales and balances. The assistant chief of the office is an alternate member of this committee.

Research Associate Program

The research associate plan is an arrangement under which technical,

industrial, and commercial organizations can support work at the Bureau on projects which are of special interest to them, yet of sufficient general

interest to justify use of Government facilities. Research associate projects

must not only be of value to all groups concerned in the particular field

and to the Federal Government, but must also be important from the standpoint of the Nation's sum total of technologic knowledge. While the

arrangement is preferably made with an association or group representing a major part of the industry concerned, projects may be undertaken in

cooperation with single companies or individuals when the results may be

expected to be of value to the general public. In any case, the results

become a part of the public domain and are published by the Bureau.

Research workers acceptable to both parties are either assigned by the

Bureau or employed by the supporting organization, which pays their

salaries and other expenses incident to the project.

Since the research associate plan was established in 1920, more than 175

organizations and individuals have supported cooperative research at the

Bureau. Many of the projects have been extremely specific and therefore

of relatively short duration. Others, such as that supported by the Portland Cement Association, have been directed toward fundamental research

in the field; this project has been active since 1924. The American Petroleum Institute has a total of 36 research associates in two projects, one of

which has been in operation continuously since 1927. The project spon90
The internal high-speed memory (left) of the NBS Eastern Automatic Computer

(p. 63) stores orders to the computer, the numbers involved in a problem, and

the results of intermediate computations. Right: interior, showing the many

small electronic components.

sored by the American Dental Association has been in existence since 1930,

and that sponsored by the Cast-Iron Pipe Research Association has been

active since 1928.

At the close of the fiscal year 13 groups were supporting 72 research

associates at the Bureau. Cooperative projects were under way on dental

materials, fuels, commercial adsorbents, electrodeposition, corn products,

hydrocarbons, underground corrosion, cement, concrete, standards for

X-ray diffraction analysis, chinaware, porcelain enamel, and asphalt

roofing.

Scientific and Technical Groups

Through active participation in the projects of professional societies and

standardizing bodies, the Bureau plays an important part in the development of test methods and criteria, in the application of scientific discoveries,

and in fundamental research programs of a national nature. It thus aids in

developing and improving engineering standards, purchase specifications,

and building and safety codes. Bureau staff members now hold approximately 1,600 positions on committees of over 90 national groups such as the American Society for Testing Materials, American Standards Association, American Society of Textile Chemists and Colorists, American

Ceramic Society, American Concrete Institute, American Foundrymen's

Association, American Geophysical Union, American Institute of Electrical

Engineers, American Petroleum Institute, American Society of Heating and

Ventilating Engineers, American Society of Mechanical Engineers, Institute

91
of Radio Engineers, Instrument Society of America, Inter-Society Color

Council, National Fire Protection Association, Optical Society of America,

Radio Manufacturers Association, Society of Automotive Engineers, and

Society of Motion Picture Engineers.

During the year, the adequacy of a newly developed shutter for moving

stairways to hold back fire was investigated at the joint request of the

Buildings Officials Conference of America and the National Fire Protection

Association; technical data and drafts of specifications were furnished to Federal Specification and ASTM technical committees on such subjects as

clay brick and tile, asbestos-cement building products, bituminous roofing

materials, electrical refrigerators, mechanical water coolers, and air-conditioning equipment; a report on fire hazards of domestic chimneys was made to the National Fire Protection Association and another on their

draft characteristics to the American Society of Heating and Ventilating

Engineers; the American Society for Testing Materials was assisted in

developing standard methods for determining the abrasion resistance of

woven textiles, plastics, rubber, carpets, and coated fabrics; the National

Research Council was aided in the formulation of a research program for

plastic materials and products, in a review of current projects on plastics,

and in the development of improved military textiles and clothing; information essential to the preparation of a safety code for glazing motor

vehicles on land highways was given the Society of Automotive Engineers;

methods of evaluating the properties of plastic films and sheeting were developed for the Society of Plastic Industry; the American Association of

Textile Chemists and Colorists was assisted in the development of standard

methods for determining flammability, color-fastness, and water-repellency

of textiles; the American Leather Chemists Association was aided in the

development of test methods for fire resistance, bursting strength, water

absorption, water-vapor permeability, and resistance to scuffing of leather

and leather products; the American Standards Association was given data

for the formulation of performance standards for nylon hosiery; the Technical Association of the Pulp and Paper Industry was aided in the development of methods for testing paper; the Society of Motion Picture Engineers was assisted in a study of storage and preservation of films and stability

of color films; the metering of gases flowing in commercial pipelines was

studied for the American Gas Association and the American Society of

Mechanical Engineers; and cooperative services were supplied to the

Applied Physics Laboratory of Johns Hopkins University in connection with

the use of rockets for stratospheric exploration.

International Radio Conferences

The prominent position occupied by this country in world affairs has

required it to play a leading part in the work of the International Telecommunications Union, which allocates radio frequencies among the nations.

During the past year, the Bureau supplied scientific and technical advisors

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for the American delegations to conferences sponsored by the Union as

follows: Provisional Frequency Board, Geneva, Switzerland; World Aeronautic Radio Conference, Geneva, Switzerland; International Radio Consultative Conference, Stockholm, Sweden; High-Frequency Broadcasting

Conference, Mexico City; Fourth Inter-American Radio Conference, Washington, D. C. In addition to actual participation in the deliberations of

these conferences, a large supporting program was maintained in the Bureau's laboratories to supply the technical advisors with the information

they required.

International Commission on Illumination

A member of the Bureau staff served as delegate to the meeting of the

International Commission on Illumination held in Paris in June and July

1948. Bureau staff members now serve as secretary of the U. S. National

Committee, which represents the Commission in this country; secretariat

director of the Committee on Colorimetry and Artificial Daylight; chairmen of the U. S. Committees on Aviation Ground and Airport Lighting,

Units, and Standards and on Calculation of Projector Systems; U. S. representatives on the Committees on Physical Photometry, Ultraviolet Radiation, Traffic Signals, and Visual Photometry; and secretary and member

of the ad hoc Committee on Color Specifications for Light Signals.

International Conference on Weights and Measures

At the Ninth General Conference on Weights and Measures, held in Paris

October 12 to 21, 1948, the Director and an Associate Director of the Bureau represented the United States through appointment by the Department of State. The most important technical development of the Conference was the adoption of a revised text describing the International

Temperature Scale. A translation of this text has since been published in

the National Bureau of Standards Journal of Research. The Conference

also recognized formally the possibility that the basic unit of length, the

meter, might eventually be defined by reference to a wavelength of light.

One of the most promising wavelengths for this purpose is that of the green

line of mercury 198, an artificial isotope transmuted from gold by neutron

bombardment.

Office of International Relations

Scientists and engineers from other countries are permitted to participate in certain normal work of the Bureau as guest workers. The program

is conducted under procedures of the Department of Commerce and the

Department of State, in accord with such legislation as the Fulbright Act

(Public Law 584, 79th Cong.) and the Smith-Mundt bill (Public Law

402, 80th Cong. ) . The Bureau's Office of International Relations makes

arrangements for foreign scientists to be accorded guest privileges at the

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Bureau; receives official visitors from abroad; correlates Bureau activities

with those of other Federal committees handling international relations,

and assists the Bureau in its own representation abroad at international

meetings. Such a program not only strengthens the relations of this country with other nations but also permits the Bureau to keep more closely in

touch with foreign developments and provides it with additional expert

temporary staff associates.

During the last year the total number of visitors and guests from other

countries was 533. Eight directors of research institutions analogous to the National Bureau of Standards were among them, representing Belgium,

Italy, China, Sweden, Mexico, Chile, India, and Great Britain. Other

visitors included 21 directors of specialized research institutions, 125 re- search scientists and engineers, 63 university professors, 70 government

officials, 81 industrial engineers, and 3 delegations consisting of 23 individuals. In addition, 46 scientists and engineers were accepted for programs

ranging from 3 to 12 months in duration, as well as 10 trainees sponsored and

supported by the Department of State and 63 technical students of graduate

level.

Technical Session on Bone Char Research

The first technical Session on Bone Char Research was held on January

27 and 28, 1949, at the National Bureau of Standards in Washington, D. C.

Conducted jointly by the Bureau and the industrial sponsors of its work

in this field, the session was attended by representatives of sugar refiners

and bone char manufacturers in Canada, England, Scotland, and the United

States. Only those sponsors in Australia and South Africa were unable

to send delegates.

Fourteen formal papers presented as many aspects of the problems of the

industry, and discussion periods following each presentation provided opportunity for exchange of ideas on many technical questions relating to

refinery operation. One-half day was devoted to each of the following

subjects: bone char kilns, test procedures, filtration operations, and basic

research on the properties of bone char.

Approximately 9,000,000,000 pounds of raw cane sugar are refined annually in the United States, requiring the use of roughly half this weight of

bone char. Since this is obviously many times the amount of bone char

in stock, the success of the bone char process depends largely upon the

efficiency with which the char can be revivified so that it can be used

many times. Prior to 1939, detailed basic knowledge of the bone char

process in sugar refining was very meager. To fill this need, a research

program was initiated at the National Bureau of Standards for study of the

fundamental nature of bone char and other solid adsorbents. Interest in

the project has steadily increased until today industrial supporters of this

work include almost all of the cane sugar refiners and bone char manu94
facturers of the United States as well as those in Canada, England, Australia,

and South Africa. Research which cannot conveniently be undertaken by

any one of the cooperating sponsors is conducted in the laboratories of the

Bureau while problems requiring plant facilities for their solution are

studied in a number of individual refineries. The purpose of the Technical Session held at the Bureau was to inform the industry of the present

status of the research program and to permit informal discussion of problems of mutual interest.

• E. U. Condon,

Director, National Bureau of Standards.

SCIENTIFIC AND TECHNICAL DIVISIONS

AND SECTIONS

ELECTRICITY AND OPTICS

Resistance Measurements

Inductance and Capacitance

Electrical Instruments

Magnetic Measurements

Photometry and Colorimetry

Optical Instruments

Photographic Technology

Electrochemistry

METROLOGY

Length

Mass

Time

Capacity, Density, and Fluid Meters

Thermal Expansion

Dental Materials

Scales

Gages

HEAT AND POWER

Temperature Measurements

Thermodynamics

Cryogenics

Engines and Lubrication

Engine Fuels

Combustion

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ATOMIC AND RADIATION PHYSICS

ATOMIC PHYSICS

Spectroscopy

Radiometry

Mass Spectrometry

Physical Electronics

Electron Physics

Atomic Physics

Neutron Measurements

RADIATION PHYSICS

Nuclear Physics

Radioactivity

X-Rays

Betatron

Nucleonic Instrumentation

Radiological Equipment

CHEMISTRY

Paint, Varnish and Lacquer

Surface Chemistry

Organic Chemistry

Analytical Chemistry

Platinum Metals and Pure Substances

Electrodeposition

Gas Chemistry

Physical Chemistry

Thermochemistry and Hydrocarbons

Spectrochemistry

MECHANICS

Sound

Mechanical Instruments

Aerodynamics

Engineering Mechanics

Hydraulics

ORGANIC AND FIBROUS MATERIALS

Rubber

Textiles

Paper

Leather

Testing and Specifications

Organic Plastics

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METALLURGY

Optical Metallurgy

Thermal Metallurgy

Mechanical Metallurgy

Chemical Metallurgy

Experimental Foundry

Underground Corrosion

MINERAL PRODUCTS

Porcelain and Pottery

Glass

Refractories

Enameled Metals

Building Stone

Concreting Materials

Constitution and Microstructure

Chemistry of Mineral Products

BUILDING TECHNOLOGY

Structural Engineering

Fire Protection

Heating and Air Conditioning

Exterior and Interior Coverings

Codes and Specifications

APPLIED MATHEMATICS

Numerical Analysis

Computation

Statistical Engineering

Machine Development

COMMODITY STANDARDS

Metal and Ceramic Products

Textiles and Apparel

Mechanical Equipment

Packaging

Chemical Products
ELECTRONICS AND ORDNANCE

ELECTRONICS STANDARDS

Engineering Electronics

Electron Tubes

Electronic Computers

ORDNANCE DEVELOPMENT

Ordnance Research

Ordnance Mechanics

Ordnance Electronics

Ordnance Engineering

Ordnance Tests

GUIDED MISSILES

Missile Dynamics

Missile Intelligence

Missile Engineering

Missile Instrumentation

Technical Services

CENTRAL RADIO PROPAGATION LABORATORY

IONOSPHERIC RESEARCH

Upper Atmosphere Research

Ionospheric Research

Field Operations

SYSTEMS RESEARCH

Regular Propagation Services

Frequency Utilization Research

Tropospheric Propagation Research

MEASUREMENT STANDARDS

High Frequency Standards

Microwave Standards

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